Fiance is having an issue with her monitor and I have had similar issues with mine. Both using Windows 7 64bit. She has Nvidia 450 GPU and I have 2 AMD 6870's crossfired.
Every now and then her main monitor will blink off for a second or two, then turn come back on. Power doesn't go out because the monitor green light stays on. I notice this happens with my second monitor but never with my primary one on my computer.
Updated her drivers, this is a fresh install of Windows 7 with just a few things on her computer. Wondering if it's the monitor but it's not that old (probably a year old now).
Any help is appreciated.