Some issues might not be inside the computer
I don't have a 59xx Graphics card but I did experience similar problems with a visiontek Geforce 3 card that I owned. Basically I would get rolling line and flickering all the time. I swaped out cards for a different geforce card and the flickering went away. This lead me to believe that the card was bad. Then after a little while of using the new card I was starting to have the same issues.
I searched for the villian and found that a little clip side fan that I used to blow on my face was the culprit. If you moved the fan away from the computer the picture would clear up. I am not saying that noise is the only cause for these problems but it happens.
Another instance was in my dorm room if my computer was against a certain wall it was terrible... flickering like crazy, yet when I moved it to a diff window everything was fine.
So a suggestion to everybody having issues with this. Try different power outlet and different positions in your room or even a different room. And move anything that conducts electricty away from your monitor/computer (this includes computer speakers). Just test it with as little interference as you can to see whether you are just a victim of bad noise.
Edit* - just for the record I now own a Radeon 9800 Pro and have not experieced any flickering, but then again I will not be in my dorm room until the end of August.
Just my 2 cents,