It this a new card? If not, those artifacts are indicative of a failing video card. I also presume taht is an unpowered PCIe card? I'd seriously consider buying an Nvidia 7900gt as the prices have really fallen with the release of the 8800's. You won't be disappointed and that card will provide excellent game play at most every setting!!!
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.