i know a lot of people suggest this, but since none of you said you tried it i thought maybe it'll help:
Video Card Drivers - always make sure you have the latest. If you already do, uninstall them, and do a clean re-install. if that doesent help try a previous version of drivers. if you're still out of luck start looking at updates for other components (chipset, BIOS, etc.) -i had this issue and for me the BIOS update did the trick, i have no idea why and how, but at least it works now :D
If this helps, please click the white XP button and to give me some XP.
If this solves your question, click the green solution button and mark it as solution so it can help others with the same problem.