I have a computer where the monitor sporadically goes blank for 20-30 seconds at a time. It started out doing this maybe once a day, but now it does it 15-20 times a day. The computer takes no input when the monitor goes blank which leads me to think it's not the video card either. I switched monitors with another computer and the new monitor did the same thing. It can go blank at any time, even when being actively used. Any suggestions?