[SOLVED] Gnome3 desktop not using entire screen

[iceaway]

I'm experiencing a very strange problem with my Gnome 3 desktop. It is not using the entire screen. I.e. the top menu ends at approximately 2/3 of the screen width. Another more annoying issue is that the application windows always are on top of the menus, which means that starting new programs is very difficult. The screen resolution is fine but the bounds of the gnome desktop seems to be off. Any ideas what could be causing this?

See http://windestam.se/screen1.png and http://windestam.se/screen2.png for screenshots.

Update:
The problem causing this was that X thought I had a second monitor connected. This was not visible from the Gnome3 display settings, but if I checked using xrandr both HDMI and VGA outputs were activated. When I disabled the VGA output everything was back to normal again.