I have almost the same problem in Xubuntu (Bug #652731) but here it is "xfsettingd" not running (which means appearance settings cannot be changed).
However if I boot from the live cd, everything works and xfsettingsd is running as it should. I use the nvidia non-free driver also, but the bug persists if i deactivate it so I'm not sure if it is releated.
I have almost the same problem in Xubuntu (Bug #652731) but here it is "xfsettingd" not running (which means appearance settings cannot be changed).
However if I boot from the live cd, everything works and xfsettingsd is running as it should. I use the nvidia non-free driver also, but the bug persists if i deactivate it so I'm not sure if it is releated.