Keyboard freezing, Computer crashing, what's happening?

Hey everybody, new to the forums here.

I am working with a macbook pro, 13 inch.

So i do not have an external mouse, i use the trackpad. Recently, it tends to freeze on occasion. If I leave it alone for a minute or so, it will unfreeze. Also, if I apply some force where the click button is, that seems to speed up the unfreezing process. When my trackpad freezes, the whole keyboard is frozen, Caps Lock won't work, control+apple+escape doesn't work, the only button that works is the power button if I feel I need to emergency shut down the computer.

Also, When I shut down my computer at night for the past two nights, I take out the power source. When I go to turn it on again, it won't turn on? The first day I freaked out, thought I would have to bring it in, but like 10 minutes later it turned on. Same happened this morning.

ALSO, I more and more frequently am getting that signal that comes up in a couple different languages that tells me my computer froze and I must hold down the power button to power off my computer and turn it on again?

I have never had a problem with this computer! (purchased at the end of 2006), I have diskwarrior, which I used very recently, and it is of course less than one percent that needs to be fixed.

Are these all related? Do I have a virus or something? What is happening to my mac?!

Thanks all in advance for the help!

~ Naz

My PowerBook G4 12" has been having trouble with the trackpad freezing and not coming back until I reboot. It seemed to start when I did an update a few weeks ago that included an upgrade on iTunes. When I notices that the problem was especially bad when iTunes was was open I reinstalled iTunes and the problem went away. Unfortunately I was prompted to do another update earlier this week and the problem is back with a vengeance. As iTunes wasn't part of the update this time and everything's been fine since the reinstall I assume it's something different. I've run another update (including a security update, etc.) and have updated Firefox but the problem is still persisting. Also, (this happened before too) when the computer is plugged in, if I try to put it to sleep it will immediately wake up--if I've put it to sleep by closing it, it will just cycle through going to sleep, waking up going to sleep, waking up...

Anyone else having this problem?

In looking around on support.apple.com I found this: http://support.apple.com/kb/TA25889?viewlocale=en_US which suggests that such a problem could be related to needing to reset the PMU. However, given that it seems to be related to an update, would that make any sense? Also, the article on resetting the PMU (http://support.apple.com/kb/HT1431) stresses that you should do so only as a last resort - what will happen when I reset it? How much will be affected?