Hey,
I've got this really annoying problem in my cab, one of my USB devices every now and then (actually fairly often) isn't working when I boot up. The reason is its driver gets corrupted; I can fix the problem by uninstalling the device in device manager and then scanning for new hardware - it finds the hardware, installs the driver and starts working fine. Unfortunately, to do all this requires a keyboard.
Do you think the problem could be the USB device or its driver? Or something else? I can't finish my nice little arcade machine with this problem occuring.
Thanks!