Since it was working then did that, it does look like the card is giving up.
If you are getting it on the desktop, something is wrong.
I am going to have to say to as said above too(driver,reseat,check the cables).
It should not be the actual monitor cable since if it was the screen would not have the artifacts.
I have seen drivers cause this, but you said it just suddenly happenedhttp://img441.imageshack.us/img441/8294/screenshot2008061416114hn3.th.jpg
Beat that driver glitch.