Still getting the error below with 3.6.4:
[2013-10-21 20:26:13] BAL0: GetResults failed no data returned (err=0 amt=0)
Using USB 2.0 ports directly on the motherboard, restarting CGMINER seems to fix the issue. Tried different USB ports, same issue. Can happen 20 minuter or hours after CGMINER.
It's possible you're having a hardware issue that only shows up after it's been under load for a while. I had this sort of failure with a bad power brick on a single.