I recieved "invalid extent entry" while running fsck in safe mode after installing iTunes and QuickTime 6.2. Was running 10.2.5. QuickTime content was crashing Safari, half my apps would not launch, and experienced frequent kernel panics.
fsck could not repair the damage, and I could find no real info at Apple or Google, so I backed up, reformatted and reinstalled OS X 10.2.4.
I was due for a backup/reformat anyway, but WFT Apple?