Double check to make sure you southbridge chipset fan is working or if it is passive cooling that it is gettin airflow. Also you can try putting an exhaust fan near the chip on the xfi sound card. The southbridge chipset controlles your pci slot so if its overheating that could be a reason for that issus. I know this from personal experience.
Phenom 9850 x4, Asus MVP Deluxe , 8gigs OCZ ddr2 1066, Visiontek 3870x2, Xfi Elite,2x WD Raptors 10k in raid 0,Antec 1000watt, and Cooler-master Stacker 830 Evolution.