LED 24 inch goes randomly black

I have dual screen display. Two 24 inch dell st2420Ls are running dvi-d with the graphics card NVIDIA GeForce GTX 670. This happens at random intervals, but basically only the screen on the right goes completely black, with the white power LED still on (not orange like it's asleep) and the screen on the left is always perfectly fine. I swapped cables from one monitor to the other, changed graphics cards, downloaded new drivers, and still the same problem. If I turn the blacked-out screen on and off it turns on completely fine, but that is the only way it brings back a picture. It's driving me nuts because i'm not sure if its my computer's settings or the monitor itself. Or maybe I have a bad power strip? I really hope someone can lend me some suggestions!   here are my specs:

Intel core i7 870 @2.93Ghz
12GB RAM
64-bit OS Windows 7 Home Premium
600W Corsair power supply
Nvidia GTX 670 4GB Superclocked
1TB Hard drive
Dell ST2420L x2