Every so often my monitor (LCD TFT thingy from Hanns-g) is going off with a message saying "Input Signal Out of Range" - and I have to restart my PC to make it work again. I have tried it on 2 monitors, and it happens on both. But it happens very randomly. Like it could work fine for 2 hours, then go off. Or it could work for 20 minutes and go off.
Try reducing your refresh rate... This happend to me once when I pushed my resolution and refresh rate a li'l up the limit.