I have an similiar problem, but my DeusEx MD crashes to freeze.
It happens after 5 min or 1 hour of playing, screen gets black or brown, the sound continues for 10 seconds normal and then hangs to a loop.
Have to hit the Reset button.
I displayed CPU und GPU temperature on second monitor, but both stay cool below 55° C.
System:
FX8150 on Asus M5A99x evo, 16GB G.Skill Ares, sapphire Fx470 8GB, WIN 7 SP1, 560 W PSU