A Graphics Problem when trying to play or watch videos

Hello, I'm having a graphics issue and I was hoping someone here knows about it. Today when I started watching a video the screen went black and there was an error message:

"Display Driver NVidia Windows Kernel Mode Driver, Version 290.36 stopped responding and has successfully recovered"

Since then whenever I try to play a game there are green dots on the screen or it just goes black with "white outlines" on the words...just weird artifacts like that. The game either doesn't respond or just crashes soon. The same happens when I try to watch a video. If it's windowed it works with an occasional green dot, but if I make it full screen there are many dots. I uninstalled the beta driver completely and reinstalled the "older" 285.62. The same happens.

Is this hardware related? My video card is a GTX 560 and it's still under warranty. I haven't had any problems with it before. This is completely out of the blue.

I have the exact same issue with my Radeon HD5850 when I drastically overclock the card for a game, then forget to reset the clocks before watching a video online. That's why I think it could be an overheating issue. But it's good to hear that things are back to normal for now.