hmmmmmmmmm........1024X768? That doesn't make any sense. You stated above that you couldn't run at 1280x1024. I'm confused. Unless your video card is going down the tubes, that resolution is the most common next to 800x600. Check your monitors refresh rate and set it to the highest (85+) and also use 32 bit true color. Otherwise I would use driver cleaner (free download) and remove your current ATI drivers and reinstall the latest ones for your card.
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.