My iMac froze for the fifth time today, so I called up AppleCare at 1 (800) 275-2273 and talked with Josh. If you call them, have your computer’s serial number ready. It’s the first thing he asked me for, and I don’t think they’ll say anything without it.

Anyway, all we did was restart the computer with the first install disc in the drive, run Disk Utility, Repair Macintosh HD, Repair Permissions, and restart. He said this happens, and this usually fixes it. He also noted that this can be caused by corrupt system files, and this can happen during system updates.