It could be your monitor is starting to die, but you should try the following:
1. Reinstall the drivers.
2. Disconnect the video cable at both ends, then reconnect
3. Try to borrow another cable in case it's an issue with the cable
4. Re-seat your video card unless it is an integrate video chip. That means pull the video card out of the slot, then re-insert the card.
If nothing changes, then it appears the monitor is the issue.