I'm a newbie and I just built my first pc and everything runs fine except when I render in 3ds max. The CPU temp is 50c and the motherboard goes to about 47C anf then it just freezes. I downloaded the Doom 3 demo to test the load out and even when it reaches those temperatures it doesn't freeze.
my specs are (there is no overclocking yet since i need to make sure it's stable first):
Asus P5N32-SLI Premium
Corsair TWIN2X2048-8500C5 2GB Kit DDR2 X2
XFX PVT80FSHF9 GeForce 8800 GTX 768MB
Coolermaster RR-LCH-P9E1 Hyper L3 Silent CPU Cooler
Thermaltake W0104RU Toughpower 650W
Thermaltake A1927 DC Fan Series
Raidmax X1 ATX909WBP Mid Tower
I've let the system on for hours and it doesn't overheat by itself.
I had what sounds like the same problem with my P5ND2 SLI, apparently caused by the northbridge overheating (the top most Passive Heatsink on the mobo). My initial mobo would freeze within 30 seconds of initiating a benchmark or 3d game, but would never freeze on a memory or CPU benchmark. The motherboard temp never seemed to get very high according to my monitors, but apparently it was.
After getting a replacement P5ND2 it would still freeze, although it would last 45 seconds or longer before freezing. I then placed a box fan on the open case to ensure it had plenty of air, and it did not crash. I eventually replaced the stock heatsink pad with some thermal compound, and I can typically run it without the fan now.
My advice would be to get something to increase the airflow across the northbridge to check if thats the issue