Well, looks like the hard disk went -- tried to boot TC today and it would hang before it loaded extensions. After a bit of fiddling found out the hard drive was timing out. Since I don't have TC installed on the hard drive (it always sounded flaky), disabled the IDE (or something) and now TC boots. Occasionally a shot in the dark hits the target, I guess.
edit: Well, I thought it was OK, but it sounds like the hard disk is still being accessed (no light though). Guess I'll have to disconnect it completely...
OK, disconnected the hard drive and re-enabled the IDE (or whatever); seems to work.