A co-worker came to me with a weird one. She said her Mac wouldn't let her delete files unless they were created today.
So we checked it out. Sure enough files and folders on the Desktop and other places we tried gave and error hfs_swapBTNodeoffset 66 and 67 out of order error -36.
The console gave a us a clue: it said on the volume sam. Curious. Further checking showed she was using FileVault and it seems to be a file mounted at login (like loop) that is an encrypted file system. So I tried turning off FileVault and got an error saying we needed another 4053GB to remove it (yes 4TB on a MacBook with a 60GB drive) so maybe there is some corruption there.
However even though it didn't turn off, this seemed to fix the problem. We'll see tomorrow if it still works but it look as if when she logs out filevault does something to the files and they can no longer be deleted.