A short on the 5V USB bus. If the board fried then one could argue the board didn't meet the USB spec.
Either way both the board and keyboard are now suspect.
"can staples under the keys short out the key pad?"
Yes. I'd not issue a laptop to such an owner.
this happend at work, an XP operating system. Using a Targus Keypad USB 1.5Mbs. Occasionally the keys stop responding. One fix is it unplug the USB cord and then plug it back in. (front USB connector) We have done this several times but on this occasion the motherboard fried.
Additional data, key pad is in high use environment and it is common enough to work the keys faster than the product software which may or may not account for the occaisional key failing to respond. Also staples get under the keys. PAUK10 is the Targus retail number.
My questions are, can staples under the keys short out the key pad? or can USB devices cause spikes in systems? Keypad draws 5 volts. Can a non responding keypad cause the computer to not reconize the device and thus spike the power supply upon plugging it back into a running computer?