Steal the video card out of your own computer, put it in his. make sure you do proper driver installs.

Test.

BFG decided to extend his warranty and he already RMA'd it. We're waiting to see how that goes.

I have noticed that once it crashes, the reset button takes about 5 seconds to work. I find that kind of odd. Maybe motherboard. Maybe paranoia.

Brand new video card, same problem. Installed a new heatsink incase that was the problem, temps lowered by about 10 degrees, still same problem though.

Completely out of ideas.

The problem seems invariably reduced to either the PSU or the motherboard. Aieris made an RMA for the PSU with the manufacturer so we're waiting on that now.