Our buddies over at the [H] have concluded that it's not possible to overclock your 9500Pro or 9700 amateur without modifications.
Increasing or decreasing the clock of the card brought anomalies... A hex value in the BIOS was the limiting factor, so "all" that you need to do is to reflash the card with the modified BIOS and you are ready to go...
Probably ATI are doing this to prevent 9700 amateur buyers from getting a Pro out of their card (like what is possible with Nvidias TI4200)
However it isn't good news for us overclockers though :(