Can't run monitor at any resolution higher than 1280x960

I have a X1950GT 256MB AGP, and I can't set anything to a higher resolution than 1280x960, any idea why? I tried drivers version 7.10 and 8.10 and both made no difference, the screen just goes black when I try. Its been like this for a few months but now I'm getting tired of this low resolution. I had a GeForce 6800 GS before this and it worked all the resolutions my monitor supported. Any one know why?

No, but what I did was uninstalled all the drivers with a driver cleaner, installed drivers version 7.10 again, and it works at 1680x1050 resolution, but now theres some weird problems where the screen like jumps up and down really fast, I forgot what that problem was called but I think it started with a S, any one know how to fix that problem now?