I have a very old external firewire drive 40GB. http://www.amazon.com/SimpleTech-SIMPLEDRIVE-DELUXE-STI-USB2F-40/dp/B00006HVHC When I connect it with USB the drive shows up in Finder. It needs an external power supply. When I borrowed my friends 6 pin to 6 pin Firewire cable the drive shows up in Finder and needs no power supply. Cool. I bought an inexpensive Firewire 6 pin to 6 pin cable, plug it in. No Drive in Finder! When I use USB it appears! Works fine. I am sort of assuming my cheap Firewire cable is the problem. Would you agree?