you need to run Diskwarrior on your internal drive. almost 90% of the time when i have a recognition problem with my fw hd's it's due to problems with my main hd. sometimes both need fixing, but usually everything goes back to normal after the main is fixed. one trick with diskwarrior (and yes you're going to need to boot to os 9 to run it), is that if you launch it and then plug in your problem drive, 99% of the time it will find it and be able to repair it which might do the trick, but i'm guessing the main drive is the problem if the fw drive works on the other mac.
20" 2ghz iMac G5 | 2GB ram | os 10.4 | 15" Ti PB 867 | 1 gb ram | os 10.3.9 | grape imacDV 400mhz | 512 mb ram | os10.2.8/9.2.2 | smc barricade router w/sbc yahoo dsl | HP psc-2355 all-in-one printer | graphire2 | Living happily ever after, every now and then