While testing a new computer I had three different flash drives burn out as soon as I inserted them. These had all previously worked perfectly on several other computers. One was almost new.

Other similar flash drives have been unaffected and a USB mouse also works fine. Motherboard connections and voltages appear ok. Can anyone tell me more about this, or explain what can cause flash drives to fail in this way? Why do some die immediately while others appear unaffected? Obviously I don't dare trust this machine any longer. Until now I didn't think it was even possible to destroy a USB device in a properly connected port.

I had a similar experience with flash drive that I thought had died. I even sent it back for a new one and found it also would not light up. When I tried it in other computers, it worked fine. The best I could surmise is that it required more voltage than my USB ports delivered. I have about five others that work fine, but not this one (Crucial 512 Gizmo!). I can't fault the company, they stood behind their product. I just haven't gotten around to relate my experience with the new one yet. Some how the USB connection or the replacement power supply in my computer may be the real problem.

It is possible that front panel ports may be incorrectly wired, one thing to try is, perhaps, a USB-powered fan, to see if it runs, and runs in the right direction.

Have any other devices worked on the same port?

That's possible Matth. Maybe this person hooked the USB wiring up wrong to the mobo.