Ok cool. Thank you for the info.
Let's try this. Go into your applications folder. Inside the applications folder, you should find another folder called Utilities. Go inside Utilities and you'll be looking for a program called Disk Utility. Open it. In the left hand window area, make sure your hard drive is selected. It's probably called Macintosh HD unless you renamed it. At the top of the program, make sure you are in the First Aid tab. Now you're going to look for a button called Repair Disk Permissions. Click it and let it do its thing. Depending on how big your hard drive is and how much stuff you have on it, it could take a while. If it finds any errors, that white window will fill up with a bunch of weird things, don't worry about it. As soon as it is completed, restart your computer. Once you're back into your desktop, try updating to 10.8.3 and see if it works.
Let me know if it works or if you have any questions about these steps.
Cheers
Searay