have you added any hard drives? (firewire, scsi, etc..) an obscure bug bit me when I added the scsi rack back onto my system, and SOME iLok auths would fail (not all, but mach5, Phoenix and other non-Digi auths). when I removed the "new" hard drives, all was fine. Some kind of permissions issue. at the time, it was my older G4/867 os10.3.4, PTHD3 accel. PT 6.4cs9 removing the scsi drives from the chain solved it. adding them back broke it. I reported this to tech support.