I can't overclock my HD4670. Using AMD's tool, if I raise the core 10MHz, the screen goes nuts with artifacts. Overdrive lets me overclock, but only 20MHz, before I max out the bar. Any advice? I think it might be because the card is in 2D mode when I am trying to apply the clock speeds, but I can't figure out how to get the card into 3D mode when I am overclocking.