Power went out now have problem with monitors

I have a 22in and a 24in running on dual 7900gts. After the power went out today I turned my computer back on and everything was fine untill i turned both my monitors off and went and did something for a while. When I came back to turn them on they both said no signal and shutoff, i can turn them off then on fast and and they come on but if I turn them off for a while then turn them on it says no signal. I have a button on my keyboard that I push to switch users in windows, when I push the button both my monitors come back on. Also just updated to the latest video card drivers thinking maybe that would fix it but it didn't. Seems like I always get the strange problems i've never seen before.