I have an xfx gt240 512 MB DDR3 and I am using msi afterburner to overclock it
It doesn't seem to matter what I set it too, none of my benchmark tests how any difference from the stock settings
As for frame rate, I'm not too sure, but make sure you are hitting apply after designing you OC profile. If that doesn't work, save it to a profile and load it from there. You should try 3D Mark Vantage (DX10), to bench it because it gives you graphical scores. I overclocked my card from 797MHz (1950MHz Mem.) [scores about P6100] to 900MHz (2004MHz Mem.) and got around P6700 in 3D Mark 11 (DX11). Keep in mind that your card is a DX10 card and can only be benched by programs running a DirectX 10 engine.