If your Mac won't boot, try here first !
This is from an Apple Support Document...
Nothing can be more frustrating than turning on your Mac only to find that it won't start up. Instead of seeing the Finder, you see a blue or gray screen, an icon of a broken folder, a kernel panic, a flashing question mark, or a computer that just sits there. What can you do? Don't worry. It could be a simple issue that you can fix yourself.
You see an empty, blue screen. You might also see a progress indicator, which looks like a colored pinwheel or spinning disc. The spinning beachball of death.
There are several different things you can try to fix this symptom. Go through each of them one by one until you find the solution. Some of them are advanced techniques, but give them a try.
Mac OS X reviews fonts in the Mac OS 9 System Folder as it starts up. A damaged Mac OS 9 font file can cause this issue.
Tip: Install Mac OS X 10.2.4 or later to avoid this issue.
Start up from your Mac OS 9 System Folder or a Mac OS 9 CD-ROM disc. If your computer only starts from Mac OS X, start up in Safe Mode.
Drag the Fonts folder from the Mac OS 9 System Folder (not the Mac OS X System folder) to the desktop.
Restart the computer in Mac OS X.
Remove incompatible third-party startup items.
Start up from your Mac OS 9 System Folder or a Mac OS 9 CD-ROM disc. If your computer only starts from Mac OS X, start up in Safe Mode.
Open the Mac OS X hard disk.
Drag third-party items out of the /Library/StartupItems and /System/Library/StartupItems folders. You may wish to temporarily store them in the Mac OS X Users folder. If you're unsure whether an item is a third-party item or an Apple-installed item, don't move it.
Restart the computer in Mac OS X.
An incompatible login item could cause this symptom.
For Mac OS X 10.2 or later, start up in Safe Mode.
From the Apple menu, choose System Preferences.
From the View menu, choose Accounts then click Startup Items. In Mac OS X 10.2, choose Login Items from the View menu.
Select all the login items and click Remove.
From the Apple menu, choose Restart.
If this resolves the issue, add the login items one at a time until the symptom occurs again. That way you'll know which one is incompatible. Repeat these steps and remove the incompatible item.
Selecting the "Connect automatically when starting TCP/IP applications" option in Network preferences can sometimes cause this issue. You'll need to delete the preference file that holds this setting. This is an advanced step that will reset all of your computer's network settings. You will need to reconfigure them in Network preferences to reconnect to the Internet or a network.
Start up the computer in Single-User Mode.
Type: mount -uw /
Press Return.
Type one of the following:
(for Mac OS X 10.2.8 or earlier)
mv /var/db/SystemConfiguration/preferences.xml preferences.old
(for Mac OS X 10.3 or later)
mv /Library/Preferences/SystemConfiguration/preferences.plist preferences.old
Tip: There is a space between ".plist" and "preferences.old".
Press Return.
Type: reboot
Press Return.
If your computer still starts up to a blue screen, follow these steps.
Start up the computer in Single-User Mode.
Type: mount -uw /
Press Return.
Type:
mv /Library/Preferences/com.apple.loginwindow.plist preferences2.old
Tip: There is a space between ".plist" and "preferences".
Press Return.
Type:
mv /Library/Preferences/com.apple.windowserver.plist preferences3.old
Press Return.
Type: reboot
Press Return.
Reset certain privileges.
Start up the computer in Single-User Mode.
Check the volume with fsck.
Type: mount -uw /
Press Return.
Type: chmod 1775 /
Press Return.
Type: reboot
Press Return.
Important: If any of the steps above resolved the issue, stop here.
If Mac OS X automatically logs in for you (you don't have to type your password when you turn the computer on), follow these steps. Otherwise go to step 8.
Start up the computer in Single-User Mode.
Check the volume with fsck.
Press Return.
Type: mount -uw /
Press Return.
Type: cd /Users/[affected username]/Library
Tip: Instead of "[affected username]", type the username for your account, or the account that is experiencing this issue. For example, if the username is "theta," type:
cd /Users/theta/Library
Press Return.
Type: mv Preferences Preferences_old
Press Return.
Type: mv Caches Caches_old
Press Return.
Type: reboot
Press Return.
If you can now successfully start and log in, use the following steps to isolate the issue:
Open the Console utility. It's in the Utilities folder (/Applications/Utilities).
From the File menu, choose Open Log.
In the goto field, type: /var/log/system.log, then click the Open button.
From the Edit menu, choose Find.
In the Find window, type "parse failed" and click the Next button.
Look for log entries that are similar to the following:
{date} Dock[500] CFLog (0): CFPropertyListCreateFromXMLData(): plist parse failed; the data is not proper ISO-8859-1. The file name for this data could be: com.apple.dock.plist -- /Users/us/Library/Preferences/ The parser will retry as in 10.1, but the problem should be corrected in the plist. {date} trident crashdump: Crash report written to: /Users/us/Library/Logs/CrashReporter/Dock.crash.log
For each "parse failed" message that you find, remove the matching .plist file from the ~/Library/Preferences_old folder. The tilde "~" character represents your home folder.
Repeat steps s and t until you have removed all of the .plist files associated with "parse failed" messages.
In the Finder, rename the ~/Library/Preferences folder to "Preferences_new".
Rename Preferences_old to Preferences.
From the Apple menu, choose Log Out. When the login panel appears log back in.
Important: If the issue is resolved, stop here. Otherwise, skip to step 9.
If you log in each time the computer starts up, do the following:
Start up the computer in Single-User Mode.
Check the volume with fsck.
Press Return.
Type: mount -uw /
Press Return.
Type: cd /Users/[affected username]/Library
Tip: Instead of "[affected username]", type the username for your account, or the account that is experiencing this issue. For example, if the username is "theta," type:
cd /Users/theta/Library
Type: mv Preferences Preferences_old
Type: reboot
Press Return.
If you can successfully login, use the following steps to isolate the issue:
Open the Console utility. It's in the Utilities folder (/Applications/Utilities).
From the File menu, choose Open Log.
In the goto field, type: /var/log/system.log , then click the Open button.
From the Edit menu, choose Find.
In the Find window, type "parse failed" and click the Next button.
Look for log entries that are similar to the following:
{date} Finder[500] CFLog (0): CFPropertyListCreateFromXMLData(): plist parse failed; the data is not proper ISO-8859-1. The file name for this data could be: com.apple.HIToolbox.plist -- /Library/Preferences/ The parser will retry as in 10.1, but the problem should be corrected in the plist. {date} trident crashdump: Crash report written to: /Users/us/Library/Logs/CrashReporter/Finder.crash.log
For each "parse failed" message that you find, remove the matching .plist file from the /Library/Preferences_old folder.
Repeat steps o and p until you have removed all of the .plist files associated with "parse failed" messages.
In the Finder, rename /Library/Preferences folder to Preferences_new.
Rename Preferences_old to Preferences.
From the Apple menu, choose Log Out. When the login panel appears log back in.
If the issue persists, follow the steps for "You see a blank, gray screen" below.
A "broken folder" icon, a prohibitory sign, or "kernel panic" message appears
When a kernel panic happens, white text on a black background is drawn on top of the last video image on the monitor before the panic occurred. You may see a message that begins with a phrase like "Unresolved kernel trap".
The prohibitory sign, pictured here, appears instead of the "broken folder" icon in Mac OS X 10.2 and later.
This symptom usually occurs when a file or folder has been moved, replaced, or damaged. It could also occur if you use certain hardware or software with your computer. The steps to fix this symptom are in another article titled, "Mac OS X: 'Broken Folder' Icon, Prohibitory Sign, or Kernel Panic When Computer Starts Up". Try the steps in that article. If they don't solve the issue, try these steps:
If you're trying to start up from a Mac OS X installation CD, make sure it's not too old to be used with your computer. Later model computers can't use earlier versions of Mac OS X.
If you've renamed or moved system-installed folders, such as Applications, System, or Library, return them to their original location or rename them using their original names.
Don't modify the privileges of Mac OS X system files. Doing so may cause kernel panics.
These hardware items may produce a kernel panic message during startup. If one of them is installed, check to see if it's causing the issue.
AirPort Extreme card
Matrox RTMac card
128-Bit 2D/3D Professional Graphics Card
PC Card modem
The installer for an application you recently installed could have caused this issue.
If the issue occured after you updated to Mac OS X 10.2.1, see this document.
Mac OS X 10.3 only: If the issue only occurs once in a while (intermittently), do this after a successful startup:
From the Finder's Go menu, choose Go to Folder.
Type the following without quotes: "/System/Library/Extensions/".
Press Return.
In the Extensions window, locate the file named BootCache.kext.
Delete the BootCache.kext file. You may be prompted for an administrator password.
The next time you start up, the startup process could take a little longer than usual as the BootCache.kext file is recreated.
If the issue still occurs, follow the steps for "You see a blank, gray screen" below.
You see a blank, gray screen
Make sure the latest firmware for your computer is installed. Check Apple Downloads for the latest versions.
Disconnect all peripheral devices, except for the Apple keyboard and mouse. This includes ADB, serial, USB, FireWire, SCSI, and PCMCIA devices. If this resolves the issue, connect one device at a time, restarting after each one, until you've determined which device is causing the issue.
Remove third-party hardware upgrades such as memory (RAM), microprocessor upgrade cards, and PCI cards. If this resolves the issue, add back one item at a time, restarting after each one, to isolate the issue. Note: Apple does not provide technical support for Mac OS X when used with third-party microprocessor upgrade cards.
Start up from your Mac OS X installation disc and check the hard disk with Disk Utility or, if necessary, fsck.
If you are comfortable doing so, reset your computer's Power Management Unit. Specific directions are available elsewhere in the Knowledge Base.
Additional tips may be available in this document.
A flashing question mark appears
See "Macintosh: Flashing Question Mark at Startup".
Steps for any other issue that occurs during startup
If an Ethernet cable is connected to your computer, temporarily disconnect it and restart. If you have enabled NetInfo, you may need to temporarily disable it in the Directory Setup application.
You shouldn't remove or rename any of these Mac OS X system files or folders.
Applications (a visible folder)
automount (an invisible folder)
Library (a visible folder)
mach_kernel (an invisible file)
System (a visible folder)
Users (a visible folder)
Follow the steps for "You see a blank, gray screen" above.
This is from an Apple Support Document...
Nothing can be more frustrating than turning on your Mac only to find that it won't start up. Instead of seeing the Finder, you see a blue or gray screen, an icon of a broken folder, a kernel panic, a flashing question mark, or a computer that just sits there. What can you do? Don't worry. It could be a simple issue that you can fix yourself.
You see an empty, blue screen. You might also see a progress indicator, which looks like a colored pinwheel or spinning disc. The spinning beachball of death.
There are several different things you can try to fix this symptom. Go through each of them one by one until you find the solution. Some of them are advanced techniques, but give them a try.
Mac OS X reviews fonts in the Mac OS 9 System Folder as it starts up. A damaged Mac OS 9 font file can cause this issue.
Tip: Install Mac OS X 10.2.4 or later to avoid this issue.
Start up from your Mac OS 9 System Folder or a Mac OS 9 CD-ROM disc. If your computer only starts from Mac OS X, start up in Safe Mode.
Drag the Fonts folder from the Mac OS 9 System Folder (not the Mac OS X System folder) to the desktop.
Restart the computer in Mac OS X.
Remove incompatible third-party startup items.
Start up from your Mac OS 9 System Folder or a Mac OS 9 CD-ROM disc. If your computer only starts from Mac OS X, start up in Safe Mode.
Open the Mac OS X hard disk.
Drag third-party items out of the /Library/StartupItems and /System/Library/StartupItems folders. You may wish to temporarily store them in the Mac OS X Users folder. If you're unsure whether an item is a third-party item or an Apple-installed item, don't move it.
Restart the computer in Mac OS X.
An incompatible login item could cause this symptom.
For Mac OS X 10.2 or later, start up in Safe Mode.
From the Apple menu, choose System Preferences.
From the View menu, choose Accounts then click Startup Items. In Mac OS X 10.2, choose Login Items from the View menu.
Select all the login items and click Remove.
From the Apple menu, choose Restart.
If this resolves the issue, add the login items one at a time until the symptom occurs again. That way you'll know which one is incompatible. Repeat these steps and remove the incompatible item.
Selecting the "Connect automatically when starting TCP/IP applications" option in Network preferences can sometimes cause this issue. You'll need to delete the preference file that holds this setting. This is an advanced step that will reset all of your computer's network settings. You will need to reconfigure them in Network preferences to reconnect to the Internet or a network.
Start up the computer in Single-User Mode.
Type: mount -uw /
Press Return.
Type one of the following:
(for Mac OS X 10.2.8 or earlier)
mv /var/db/SystemConfiguration/preferences.xml preferences.old
(for Mac OS X 10.3 or later)
mv /Library/Preferences/SystemConfiguration/preferences.plist preferences.old
Tip: There is a space between ".plist" and "preferences.old".
Press Return.
Type: reboot
Press Return.
If your computer still starts up to a blue screen, follow these steps.
Start up the computer in Single-User Mode.
Type: mount -uw /
Press Return.
Type:
mv /Library/Preferences/com.apple.loginwindow.plist preferences2.old
Tip: There is a space between ".plist" and "preferences".
Press Return.
Type:
mv /Library/Preferences/com.apple.windowserver.plist preferences3.old
Press Return.
Type: reboot
Press Return.
Reset certain privileges.
Start up the computer in Single-User Mode.
Check the volume with fsck.
Type: mount -uw /
Press Return.
Type: chmod 1775 /
Press Return.
Type: reboot
Press Return.
Important: If any of the steps above resolved the issue, stop here.
If Mac OS X automatically logs in for you (you don't have to type your password when you turn the computer on), follow these steps. Otherwise go to step 8.
Start up the computer in Single-User Mode.
Check the volume with fsck.
Press Return.
Type: mount -uw /
Press Return.
Type: cd /Users/[affected username]/Library
Tip: Instead of "[affected username]", type the username for your account, or the account that is experiencing this issue. For example, if the username is "theta," type:
cd /Users/theta/Library
Press Return.
Type: mv Preferences Preferences_old
Press Return.
Type: mv Caches Caches_old
Press Return.
Type: reboot
Press Return.
If you can now successfully start and log in, use the following steps to isolate the issue:
Open the Console utility. It's in the Utilities folder (/Applications/Utilities).
From the File menu, choose Open Log.
In the goto field, type: /var/log/system.log, then click the Open button.
From the Edit menu, choose Find.
In the Find window, type "parse failed" and click the Next button.
Look for log entries that are similar to the following:
{date} Dock[500] CFLog (0): CFPropertyListCreateFromXMLData(): plist parse failed; the data is not proper ISO-8859-1. The file name for this data could be: com.apple.dock.plist -- /Users/us/Library/Preferences/ The parser will retry as in 10.1, but the problem should be corrected in the plist. {date} trident crashdump: Crash report written to: /Users/us/Library/Logs/CrashReporter/Dock.crash.log
For each "parse failed" message that you find, remove the matching .plist file from the ~/Library/Preferences_old folder. The tilde "~" character represents your home folder.
Repeat steps s and t until you have removed all of the .plist files associated with "parse failed" messages.
In the Finder, rename the ~/Library/Preferences folder to "Preferences_new".
Rename Preferences_old to Preferences.
From the Apple menu, choose Log Out. When the login panel appears log back in.
Important: If the issue is resolved, stop here. Otherwise, skip to step 9.
If you log in each time the computer starts up, do the following:
Start up the computer in Single-User Mode.
Check the volume with fsck.
Press Return.
Type: mount -uw /
Press Return.
Type: cd /Users/[affected username]/Library
Tip: Instead of "[affected username]", type the username for your account, or the account that is experiencing this issue. For example, if the username is "theta," type:
cd /Users/theta/Library
Type: mv Preferences Preferences_old
Type: reboot
Press Return.
If you can successfully login, use the following steps to isolate the issue:
Open the Console utility. It's in the Utilities folder (/Applications/Utilities).
From the File menu, choose Open Log.
In the goto field, type: /var/log/system.log , then click the Open button.
From the Edit menu, choose Find.
In the Find window, type "parse failed" and click the Next button.
Look for log entries that are similar to the following:
{date} Finder[500] CFLog (0): CFPropertyListCreateFromXMLData(): plist parse failed; the data is not proper ISO-8859-1. The file name for this data could be: com.apple.HIToolbox.plist -- /Library/Preferences/ The parser will retry as in 10.1, but the problem should be corrected in the plist. {date} trident crashdump: Crash report written to: /Users/us/Library/Logs/CrashReporter/Finder.crash.log
For each "parse failed" message that you find, remove the matching .plist file from the /Library/Preferences_old folder.
Repeat steps o and p until you have removed all of the .plist files associated with "parse failed" messages.
In the Finder, rename /Library/Preferences folder to Preferences_new.
Rename Preferences_old to Preferences.
From the Apple menu, choose Log Out. When the login panel appears log back in.
If the issue persists, follow the steps for "You see a blank, gray screen" below.
A "broken folder" icon, a prohibitory sign, or "kernel panic" message appears
When a kernel panic happens, white text on a black background is drawn on top of the last video image on the monitor before the panic occurred. You may see a message that begins with a phrase like "Unresolved kernel trap".
The prohibitory sign, pictured here, appears instead of the "broken folder" icon in Mac OS X 10.2 and later.
This symptom usually occurs when a file or folder has been moved, replaced, or damaged. It could also occur if you use certain hardware or software with your computer. The steps to fix this symptom are in another article titled, "Mac OS X: 'Broken Folder' Icon, Prohibitory Sign, or Kernel Panic When Computer Starts Up". Try the steps in that article. If they don't solve the issue, try these steps:
If you're trying to start up from a Mac OS X installation CD, make sure it's not too old to be used with your computer. Later model computers can't use earlier versions of Mac OS X.
If you've renamed or moved system-installed folders, such as Applications, System, or Library, return them to their original location or rename them using their original names.
Don't modify the privileges of Mac OS X system files. Doing so may cause kernel panics.
These hardware items may produce a kernel panic message during startup. If one of them is installed, check to see if it's causing the issue.
AirPort Extreme card
Matrox RTMac card
128-Bit 2D/3D Professional Graphics Card
PC Card modem
The installer for an application you recently installed could have caused this issue.
If the issue occured after you updated to Mac OS X 10.2.1, see this document.
Mac OS X 10.3 only: If the issue only occurs once in a while (intermittently), do this after a successful startup:
From the Finder's Go menu, choose Go to Folder.
Type the following without quotes: "/System/Library/Extensions/".
Press Return.
In the Extensions window, locate the file named BootCache.kext.
Delete the BootCache.kext file. You may be prompted for an administrator password.
The next time you start up, the startup process could take a little longer than usual as the BootCache.kext file is recreated.
If the issue still occurs, follow the steps for "You see a blank, gray screen" below.
You see a blank, gray screen
Make sure the latest firmware for your computer is installed. Check Apple Downloads for the latest versions.
Disconnect all peripheral devices, except for the Apple keyboard and mouse. This includes ADB, serial, USB, FireWire, SCSI, and PCMCIA devices. If this resolves the issue, connect one device at a time, restarting after each one, until you've determined which device is causing the issue.
Remove third-party hardware upgrades such as memory (RAM), microprocessor upgrade cards, and PCI cards. If this resolves the issue, add back one item at a time, restarting after each one, to isolate the issue. Note: Apple does not provide technical support for Mac OS X when used with third-party microprocessor upgrade cards.
Start up from your Mac OS X installation disc and check the hard disk with Disk Utility or, if necessary, fsck.
If you are comfortable doing so, reset your computer's Power Management Unit. Specific directions are available elsewhere in the Knowledge Base.
Additional tips may be available in this document.
A flashing question mark appears
See "Macintosh: Flashing Question Mark at Startup".
Steps for any other issue that occurs during startup
If an Ethernet cable is connected to your computer, temporarily disconnect it and restart. If you have enabled NetInfo, you may need to temporarily disable it in the Directory Setup application.
You shouldn't remove or rename any of these Mac OS X system files or folders.
Applications (a visible folder)
automount (an invisible folder)
Library (a visible folder)
mach_kernel (an invisible file)
System (a visible folder)
Users (a visible folder)
Follow the steps for "You see a blank, gray screen" above.