did they tell you to swap the cards to see if the error followed the card or the slot?? did they also tell you to try one video card in the slot to see if the mb will see any card. also did you run the two bios patches 0906 for the new cpu code and 1015?? did asus tech also tell you to go in under advance setting and switch from auto setting in the bios to rev 2.0 then 1.0 to see if it the cards or the mb?? also with one video card in the main slot have you run gpu-z to see if the card is reading right. if it not a bent pin in the pci slots it could be a dirty card. see if there any dirt or oil on the fingers of the video cards.