My flash drive is seen, then disappears, then reappears. What should I do?

I just bought this thing about a month ago. It's an 8-gig pqi flash drive. It worked fine one second, plugged it in to a friends computer with screwed up usb ports (none of them work very well), plugged it back in to my computer: the thing constantly connects, then disconnects, in an infinite loop. I can't diagnose it, because it isn't seen by the computer long enough to run diagnostics. I think it has something to do with the drive's drivers, but am not sure. There doesn't appear to be any physical damage.