[Slick]

I troubleshot a very similar problem a few computers ago. Somewhat intermittent and seemingly impossible to nail down. I'll save you the long story, but it turned out a physical defect on the computer's parallel port. Most of the time it worked fine, jiggled the cables and everything. Then once in a while it wouldn't work for a while. Drove me nuts. I forget how I actually proved it was the port... I will reply to this thread if I remember.

Slick.