Repairing permissions, is a general "remedy" for checking your /Library/Receipts.In a few words:
Many things you install in Mac OS X are installed from package files (whose filename extension is ".pkg"). Each time something is installed from a package file, a "Bill of Materials" file (whose filename extension is ".bom") is stored in the package's receipt file, which is kept in /Library/Receipts/ . If you look in the Receipts folder, for example, you should see all kinds of files that end with .pkg, including some that were created when Mac OS X was installed (for example, BaseSystem.pkg). Don't worry, these files don't take up much disk space and you shouldn't put them in the Trash.
Each of those ".bom" files contains a list of the files installed by that package, and the proper permissions for each file.
When you use Disk Utility to verify or repair disk permissions, it reviews each of the .bom files in /Library/Receipts/ and compares its list to the actual permissions on each file listed. If the permissions differ, Disk Utility reports the difference (and corrects them if you use the Repair feature).
Taken from here:
http://docs.info.apple.com/article.html?artnum=25751
It's not necessary it will solve something.You'll have to go Applications > Utilities > Disk Utility > Repair permissions to do it. Also, in case your graphics card shows failures (check with other apps as well) you can run Apple's hardware test ( It's in your initial cd's). Finally, make sure it's not the media that provokes it.