Comment 25 for bug 577640

The error message comes from this patch to gnome-desktop:

./debian/patches/100_load_desired_settings.patch:+ "X server does not support size requested");

So, gnome is attempting to load your existing ~/.config/monitors.xml however in some situations gnome will attempt to use Xrandr 1.2 functionality (such as to arrange monitors side-by-side), which nvidia does not support (nvidia only has xrandr 1.0 support currently). Of course, the xorg.conf setting up NVIDIA has already established the desired layout so gnome's action here is entirely superfluous (and should not be attempted).

If I'm correct, then one simple workaround would be to delete your ~/.config/monitors.xml. With Twinview set in your xorg.conf you don't need a monitors.xml.

At some point NVIDIA will likely support xrandr 1.4, which is one possible way this will be resolved. I don't have a public ETA on that, but if that happens in the next few months and gets included in Precise we might consider that a "solution" (although unless Twinview is removed from nvidia (unlikely), it will still be possible to turn that on and still see this problem.)

The more proper solution, and the one I think this bug report should focus on, would be for gnome-desktop to recognize when TwinView (or Xinerama) is enabled, and in those cases don't attempt to process monitors.xml and just bail out.