Did my PSU kill graphic card??

My PC worked fine last night. Then I turned it on in the morning for about an hour and shut it down. Couple hours later when I went to play Left 4 Dead, my game froze and I got a blue screen. The PC restarted and afterwards I kept getting screen artifacts. At first, it wasn't that bad but it progressively got worse to the point where I could barley see anything.

I had recently gotten a 680 W power supply unit only 4 months ago. The power supply unit manufacturers offer a 1 year warranty so if it's their fault I want to at least get a new power supply unit. Can someone please confirm if this is most probable reason? And what should I tell them in email without sounding too rude because I'm a bit ticked off right now if it's because of their PSU...

I really don't think it's over heating issue because I barley use the PC for more than 4 hours a day, and it's very clean internally too. I can't check my CPU temps because I can barley see where I'm clicking on my screen with the graphics artifacts...

PC Specs:
2.53 Ghz intel quad core
Nvidia geforce 8800 gts 640 mb
2 GB ram
680 w power supply