Also, I'm not sure if you can figure out how to force it to freeze in the BIOS, but if you can, disconnect everything but the bare essentials and see if the issue still occurs.
That is, unplug everything from the motherboard except power, CPU+HSF, one stick of RAM and GPU (if you don't have integrated graphics available).  The only things that should be plugged into the computer would be power, keyboard and monitor.