By your comp you mean your laptop right? If it was always working before, and now it keeps appearing and disappearing, and it does this on more than one computer, then I would guess the wire or connector on the hard drive has gone faulty. It seems a reasonable hypothesis, but I'm no hardware faults expert. I've heard that those external hard drives are quite prone to breaking too.
Swith, maybe the edlug list could tell us something?
I've had it with you. If I had an image of a laser gun I would absolutely position it right here in my hand...
Ha! I have a real laser absolutely positioned in my hand!