I've been having the same type of video corruption from startup. The video quality seems to progressively be getting worse as I use my computer.
I've tested two different monitors, one CRT and one LCD, both giving the same results. I've also just recently upgraded the processor, ram, and new CD-ROMs. (I'll post all my parts at the bottom.) Also, I added a VGA cooler on my 9800 pro.
Any suggestions would be greatly appreciated. Thanks.
2600+ Barton /w Thermaltake Volcano 7+
A7n8x Deluxe Rev. 2.0
1GB 3200 Corsair XMS 2-3-3-6