Yes, CNQ can normally (?) be used with FSB overclock, but...

The Phenom IIs have 4 power (performance) states. Each pState has an associated CPU multiplier and voltage. When you bump the FSB, you risk causing an instability at any one of the 4 pStates. Sounds like you're stable at pState=0 (max performance), but probably not at pState=3 (max power save).

At a FSB 252 and pState=3, the CPU frequency is 1008MHz (up from 800MHz), but, the default voltage specified in the pState table still applies, which could be a problem.

Unfortunately, I don't know of a good way to permanently alter the voltages in the pState table.