The first thing I would try is some system maintenance off of the OS disk. Boot the system from the Mac OSX DVD (Insert the DVD and hold down the "C" key when booting). Under the "Utilities" (I think that's the one) menu, click Disk Utility. Once it comes up, select the volume (probably "Macintosh HD") and then near the bottom right corner click on "Repair Disk". After that is done, click on "Repair Permissions" just to the left of that. Restart the system and see if that helps. A 3rd party disk utility like Disk Warrior ( http://www.alsoft.com/DiskWarrior/index.... ) or Tech Tool Pro ( http://www.micromat.com/index.php?option... ) might help things alone and even repair a damaged system. If that does not fix the problem, you may need to either reinstall over the existing OS ("Archive and Install") or wipe and start over if you have nothing to save ("Erase and Install").

The Disk Utility is in the Applications -> Utilities folder and should be run periodically to keep things running well.