What's the deal?
There is a computer at work that I use a lot, a QS with a dual 933 upgrade card. Up until the latest update to OS X, I could plug my iPod into it, and it would mount.. now it won't, nor will another firewire drive we have here at work. It may not be the update to OS X, but it happened around this time..
Saw a guy on the Apple support forums with the exact same problem...
(btw, these drives work on at least 2 other computers just fine)
Reset PRAM.. but I can't think of anything else to try.
Oh, and the drives do not show up in System Profiler.