I experience issues when playing CoD Modern Warfare 3 for some time. My settings are 1920x1080 4x AA everything on Extra.
My system: Gygabyte Geforce GTX 570 OC
Asus P8Z68 V PRO
Corsair Vengeance CL9 1600Mhz 2x4GB
Corsair HX 750W
After playing sometime the screen turns gray and I have to reboot. I ran Fur Mark for an hour and monitored the GPU temps. It reached 75 degrees C at most which is nothing to be worried about. I have the latest Nvidia drivers installed. I haven't experienced issues when playing other games.