I have two displays connected to a Ge-force 210 on my Dell running Ubuntu 12.04. One is using DVI the other VGA. The DVI display had a mode for its max resolution (1680x1050) which I selected. The VGA display did not for its highest res (1280x1024). I used gtf to make a mode line, created it, added it to VGA-1 and outputted it. The display flickered and auto adjusted leaving a correct width but a stretched height.
I kept trying the auto adjust on my display. As it runs through the process the display scrolls down the stretched desktop and back to the top. When I open the monitors on-screen display it says its receiving 1280x800!, while xrandr -q says it is outputting 1280x1024 at 60hz.
This problem is likely not an xrandr problem but the screen works perfectly on a windows machine at full resolution.