I tried to load WoW and watched the temps go from 40- 58, then it crashed.
Is that high, or?
How quickly does the temperature increase. If it is a sudden increase only taking a few seconds then your GPU might be getting hot enough to reset during the time between temperature updates in whatever software you are using to measure the temperature. If that is the case, send it back as the heat sink probably wasn't installed properly.
If the temperature increases slowly, say only 2 or 3 degrees every few seconds, then its probably not the above problem. Slow brain finally thought of it this morning.