i agree with rick, sounds like a bad vid card, you can try another vid card in your system, or if you happen to have onboard video, try that? Sucks to have a bad 9800 vid card..how old is the card? did you buy it brand new with the other stuff? Maybe you can RMA it unless bought used.
maybe pull the card, do a close examination of it to make sure no parts are broken and make sure the fan is spinning when running. When you put it back in, push it in to make sure it is seated firmly.
good luck....