A new BIOS was just released that addresses this problem.
I have the exact same problem, but i am running the Phenom 945 on a Jetway HA08 )hummer) motherboard.
I have read through the string of messages and guess that I also need to update my bios... I have been on to the Jetway site and there doesn't seem to be anything there????
To summarise: mobo - Jetway HA08 - 790GX + 750SB
CPU - AMD phenom II 945
Problem - mobo picks up CPU at 800 MHZ, and no manual (in bios) or AMD overdrive tweaking can solve.
Many thanks to anyone who can solve this problem, or point me in the right direction of an improved bios.