screen after a long while freezes for 1 second and then a black screen for 2 seconds

I have a 2012 Alienware computer with the specs:
Processor- Inter(R) Core(TM) i5-3330 CPU@ 3.00GHz
RAM- 6GB
Graphics card- GeForce GT 640
I have played more than 20 different games on this computer and that never happens to me. I put my screen ration at 1360x768. What graphical setting should I change so it doesn't happen? This is very bad when I'm raiding and I could easily get killed with something if this happens.

Greeting Joe2013,

We appreciate you taking the time to report this trouble you are having to us. However, since this sounds like something requiring Technical Support rather than a bug report, I will be closing this particular thread. We welcome you to post about this concern in the "Technical Support" forums in order to seek a resolution. Thank you!

Regards,
Xetyline