I'm running LXDE on Lubuntu 11.04. When I've changed my wallpaper, from a picture to background-color, it freezed for 4 seconds, then it returned me to the login screen (it probably crashed). Doing the same on the root account yielded the same results. Finally, I've deleted my background picture and restarted. No problems at the moment. The last times I've tried this , it worked fine. What caused this?