[mhollyts]

Try going into the Device Manager and selecting the Video card and see if there is a problem reported.

Have you down loaded and Device Updates from Microsoft? If not have you down loaded any updates from then right before the screen went out?

You can go to the Manufacture web site and see if there are updates for the card as well.

Since it starts out correctly when Windows boots have you tried to change the resolution on the screen? You may have changed that to one that it does not support.

Just some thoughts.