The setup:

- Dell E228WFP display able to do 1680x1050 resolution
- Nvidia Quadro NVS 400 card
- Debian Testing, with the nvidia-glx-legacy-96xx driver version 96.43.11

The problem:

The nvidia graphics driver is not able to detect the display abilities and it ends up with selecting the "nvidia-auto-select" resolution, which is 1024x768 or a similar, inadapted resolution. Specifying HorizSync and VertRefresh in the "Monitor" section does not help.

The solution:

Putting

    Option         "ModeValidation" "NoMaxPClkCheck"

in the "Screen" section. It still selects the "nvidia-auto-select" resolution, but this times it correctly detects that the display can do 1680x1050.