It's a proven fact that some 9800 owners have the same problem. Something to do with the 8x.
NO. NO NO NO! If that were true, the 9800 PRO I had in this system would have flickered just like the 5900 did. But it didn't! The only thing I changed was the card! And its not ATI residue either, I did a fresh install for the 5900. I should have stuck with ATI.