I wasn't overclocking..but I think ATI must have been. I installed Radclock to give me access to the core and memory speeds. Then I gradually bumped it down until the artifacting went away. I had to bump the core to 317 and the memory to around the same to clear up the corruption.
I've owned five GeForce cards without a problem. I thought I'd take a chance on ATI. I've learned my lesson.
______________________________________________ Dual P5 4.75 GHZ, 5 GB QDR5600 RAM, GF\Radeon 107900 XT Hybrid 528 mb video card, 10 650 GB Hyper SCSI3 HD's in a RAID 15 array. Platinum\Aluminum alloy case w\ liquid Nitrogen cooling.