What happens if you try one card?
Not many people use the Asus A8n32 coz the layout of the PCI slots does not suit - a few had one and sold for that reason alone.
Tried one card installed at a time?
I trust that you installed windows (fresh format and complete re-install), then updates, then motherboard driver, then GPU driver then everything else.
Don't use the CD drviers that came with the product - download the latest drivers from the appropriate website.
Some issues can be created because of the order you install things - or if you are using an exisiting installation but using new hardware.
There is a software package (free) called driver cleaner that can help you get rid of drivers properly (uninstall driver, then use driver cleaner before restarting).
