hi
Daemon did you have pc_efi installed on loader?
I have phenom 9500 and always with efi instant reboot when loads efi emulator, I had to modify 10.5.2 iso to boot with old bootloader and install old bootloader after install and modify some kexts. I tried with to diferent mobos (amd 690G and nforce4) and the same result.
If your mobo works with pc_efi with phenom, maybe I will be use pc_efi with phenom...
thanks it advance