Check your GPU temp, it shouldn't exceed 75c on anything mobile or anything nvidia, or 85c on non-mobile radeons
It's a stock Mac Pro setup, so that'd be fresh! I don't even know if they have the temp sensors on the GPUs inside these rigs.
If so, should Hardware Monitor or iStat be able to read the temps from inside Mac OSX?
Dunno, I don't use OSX.