While I'm on the computer the screen goes blank, I can what's on my screen but it is so dark that you can't do anything. It's like someone put a heavy tint on my screen. I turn the screen off and on with the power button and it works like normal. This happens about a couple of times a week. My question is it the monitor or my video card. I pretty sure its the monitor, I hope, and not the video card/s. I have two AMD Radeon HD 6800 that I think are in crossfire if that makes any sense. My old computer had crossfire and I replaced three or four vid cards because the screen keep blinking on and off. Thanks for any help.