I had a problem with a SATA CD drive not showing as removable, and during my investigations upgraded from BIOS f6 to f7g, at the same time resetting the CMOS. The system became unstable (it kept locking up), so I went back to f6, but the instability remains.
I have a memory from when I bought this motherboard of having to set a CMOS parameter (voltage?) to a non-standard value, but I can't remember what it was! Note that the default voltage setting for the Intelligent Tweaker in the BIOS is NOT on Auto, but setting it to Auto does not help.