If it just popped up out of the blue and only under 3D load, the first suspect would be the PSU. If that is the same Widetec POS I saw Here
, it has 2x 12v rails at 21A peak each, which is most likely only a 500w unit. Get a good quality SeaSonic or Enermax made unit (includes Corsair, Sapphire, and PC P&C) at 550w and I bet your problem will disappear.
ASUS Sabertooth 990FX/Gen3 R2, FX-8350 w/ Corsair H60, 8 GiB G.SKILL RipjawsX DDR3-2133, XFX HD 7970 Ghz, 512GB Vertex 4, 256GB Vector, 240GB Agility 3, Creative X-Fi Titanium w/ Creative Gigaworks S750, SeaSonic X750, HP ZR2440w, Win 7 Ultimate x64