I tried starting up my machine after a normal shut down the night before. Someone hit a telephone pole about 4AM and I had a tripped A/C breaker, and a burned out stove top light bulb along with a dead PC. Before all this happened I had been hard pressed to explain why my Microsoft optical USB mouse was slowing down on screen. The cursor simply wouldn't move as much anymore. I replaced the mouse with a Logitech optical USB mouse, and it worked fine. I know I had my computer maxed out with 6 additional USB ports, lazer led, and 2 CD-ROMS. Still if there was a spike in the electric line, it could've fried the motherboard regardless of load.
I have a P-4 motherboard light on between rimms, which means the board is getting power from the old PS. I bought a new PS and have installed it already since I could not get the fan to spin on the old PS. My next move is to send back the motherboard to the vendor. The biggest hassle is of course going without my PC while I try and trouble shoot it. And even if you take it to say COMPUSA or Best Buys you will be on hold for parts.