I'm a film composer in the middle of a deadline, and my G5 crashes... won't boot again, only get grey screen with Apple and spinning logo. Boot from Applecare disk, run tech tool, hardware fine, disk is corrupted. Catalog B-tree stuff. Cannot re-build without destroying data. Of course I have a clone of my system drive and try to boot from that, but IT is corrupted too of course! Go to Apple Store (I have ProCare), then run diagnostics and find the same. Advice? Wipe the drive and start from scratch. I do just that. I own about 35 plug-in instruments for Logic 8, so it took two days. The same thing happens. Disk won't boot. Talked to Applecare, they suggest buying a new internal HD, which I do. Installed it, formatted it, spent 3 more days installing all my software. guess what. The new disk won't boot. Tried to run disk repair, am told the disk is not repairable!!!!!!!!!! GRRRRRRRR Ran Tech Tool again, all hardware checks fine. Ran the Apple hardware test, same result. The Apple guy had me buy another external drive and install nothing but Tiger fresh on it to use for a master boot drive. The computer won't even boot from that now. anyway, I don't know if I'm looking for answers, venting, or sharing a nightmare situation to remind all of you how close we all are to losing valuable time, work and sanity.