ATI 9800 Bad Screen Artifacts

[2400]

I recently ripped the analogue screen cord out of my tower when the computer and screen were still running. Upon next start-up bad screen artefacts and screen flickering occurred. I have investigated heat issues, but I don't think that's the problem as it occurs form start-up. It sometimes goes away then comes straight back again as soon as I move the mouse. I also have the latest driver and catalyst control centre installed. Will I need a new video card?. If anyone has any idea on what I can do to fix this problem it would be great.