well, I'd agree, the CPU temperature does sound a little high, but most of you guys are forgetting something here. There is a difference between what the maximum CPU operating temperature is and what everybody else runs at. Sure, your CPU should usually run at 37 degrees if properly cooled, but your CPU is capable of running up to 70-80 degrees. Anyone that says otherwise needs to read up the spec sheets. The athlon 64 has thermal protection built in too, and lowers the clock multiplyer and voltage to cut the temperature in the event of overheating.
I'd focus on lowering the overall temperature of the system, and looking for other causes of this random crashing. Giving your above average CPU temperature (but within the CPU threshold), I dont think it's unreasonable to think that your graphics card is the culprit. The GF6 series run almost maxed out to the maximum temperature threshold anyway, so i'd blame that.