I have no idea how to even begin pinpointing the problem, I googled my motherboard and couldn't find any information. Usually this happens during mild-intense cpu usage (playing games or encoding media). I have a bluetooth usb receiver, logitech mouse receiver, logitech keyboard receiver, bose companion 5 (though the speakers are powered by themselves, not through the usb port) plugged in to the computer. In the middle of a game suddenly all the usb devices stop working, but the computer is still running. I even tried using row mote to control the mac and it was working fine, but the keyboard and mouse were all unresponsive. Anyone have any ideas on how to go about solving this?