Try each card individually if you haven't already, if the XFX is the main card, and Asus 2nd, and the Asus isn't showing load, then it could be faulty and causing the issue. What drivers are you using, and have you installed the latest Catalyst Application Profiles (ATI done crossfire configs for various games, link
Check out Gomez Peer
on how to make your PC work for you. Referred by dark2099 please!
Mini Rig: Biostar TP67XE / i5 2500k / Corsair H55 / 2x4GB PNY / XFX 7770 / Corsair CX500M / Win 8 64 bit / Thermaltake V9 Blackwidow