drivers are usually the biggest problem anyone has on a stable
machine. You might want to see if you can download the drivers from the
manufacturer's website.

I have an Nvidia FX-5500 graphics card, and it supports 1680x1050 with no
additional configuration (with Feisty, anyhow). Both the nv and the proprietary
driver do this.

Some stubborn drivers can be made to support such resolutions by adding
modelines to xorg.conf. You can get the necessary information from the X log.