This article is now online at macfixit:

Overlapped Extent allocation errors in Mac OS X 10.2.x: LimeWire can cause, how to fix







The peer-to-peer file sharing tool LimeWire - updated to version 3.3.4 yesterday - is apparently one cause of "overlapped extent allocation" errors (meaning that you have two files referencing the same "extend") on some Mac OS X systems.




Unfortunately, the traditional UNIX command fsck (accessible in GUI mode via Apple's Disk Utility) is unable to repair this problem, and your system can experience performance degradation as a result.




One MacFixIt reader writes: "I had two files (discovered by fsck) that had extent allocation overlaps. When I deleted some recently-imported LimeWire downloads, the problem (the extent allocation, not the kernel panics) disappeared."
Since Unix directories are simply pairs of filenames and inode numbers, you can use the following Terminal command to locate files that have overlapped extent allocations - all of them contain the inode xxxx - and delete those that exhibit the problem:

find / -inum xxxx







However, do not delete files at random. You could be erasing critical system components. Only delete files that you are sure you have recently downloaded and are not necessary to the System.




Some readers have also had success with Disk Warrior 3.0, which re-builds directory data on a disk (Apple's Disk Utility does not repair directory damage.)




If worse comes to worst, you are left with few other options than to simply perform a fresh install of Mac OS X on a formatted disk. Do not attempt an "Archive and Install" procedure. Doing so when there are unresolved directory issues can make the issue worse, and possibly lead to data loss.