ctohelpsu,
Sounds like a heating problem to me. When a system runs OK except when it's really busy, like running CPU intensive programs or specifically the burn in test it overheats and reboots or shuts itself off to prevent damage.
Check the CPU heatsing for dust bunnies or cooked thermal paste. The Chipset heatsink has also been known to cause this.
Blow out the CPU fan and heatsink, remove the heatsink, scrape old paste off with a razor blade and then clean with alcohol. Reapply new paste and see how she runs.
-Fred