I recently installed a video card (ATI Radeon x550) temporarily until my new one comes in. Since installing it, I randomly have my monitor go blank. Sometimes I can have the computer running for hours without this happening, but once it happens I can't get it to come back on short of restarting OR if I happen to have world of warcraft running at the time, I can alt+tab and most of the time it comes back on. This trick doesn't work with any other programs such as firefox or chrome so far.
The computer this card came from was my brothers, and I had forgotten that his was doing the same thing when he first tried it. His monitor has a vga cable but he had a dvi adapter on it. I took the adapter off and plugged it into the vga port instead of the dvi port and he has never had the problem again.
Could my problem be as simple as there being something wrong with the dvi connection on the video card? I've looked around at several threads with similar problems, but couldn't find a solution that fits my particular problem.
Its possible its a problem with the DVI output. Its definitely something related to the card itself since it did it in 2 different machines. I would try the VGA output if you can and see what happens. Let us know if that works. If it does, you know your problem. If it doesn't fix it, then the card is probably having real problems. BTW- make sure you have the latest drivers for that particular card, and make sure they are a version that is compatible with your OS, and that your older drivers have been completely removed.