I've got the 6800 Ultra graphics card. I left the computer running too many times and played too many games that the ball bearings on the on-board fan got nackered and started making a really annoying noise. So i taped the fan to the plastic case to shut it up and stuck a household fan next to the computer and took the side of the chasis off - which i now realise was a really dumb idea. So anyway, now my PC wont turn on and i'm 99% certain i've fried my card. If i wasn't so obsessed with top end cards i'd replace it, but to get a decent one would cost a bomb. Long story short: are graphics cards reparable? I'm pretty sure they're not but hell, buying a new one would suck.
the best way would be to try the card in another system if you can and see if it boots.... Coincedently it could be somthing else : )