First of, I have been trying to fix this problem for the past 6 hours, with tons of reboots, driver uninstalls and 'driver-cleans' using programs such as "Driver Cleaner Pro" and "Nasty File Remover".
I recently have been playing Counter-Strike: Source, every time an enemy threw a flash grenade at me, my screen would turn white (as normal) but then these distinct lines would appear. This at first was not a big issue, but got more frustrating as time went by. I decided to check the nVIDIA driver page to see if there were any new drivers for my 8600 GTS card. (Hoping they may fix this issue) There were so I went ahead and downloaded the newest one and installed. I rebooted and this is when it all started. My NVIDIA Control Panel dissapeared from my right-click menu and checking my display settings showed a very different display. Before the "Display:" would read my samsung monitor now all it says is "Default Monitor". Something also noticeable to me was the 'laggyness' of moving windows around which led me to believe that the default windows vga drivers were being used in place of my NVIDIA ones. I decided to downgrade to the 182 drivers that I still had the install for, they still cause the same problem. To further add to the mess, when I go to Device Manager and disable and enable my video cards, everything goes perfectly back to normal and works great, my NVIDIA Control Panel comes back and everything is as good as new.
My guess is that the VGA drivers are kicking in instead of the NVIDIA ones, is this a common error? I certainly have never seen it before...
Any help would be greatly appreciated. Thanks