I recently upgraded from Ubuntu 15.04 to Ubuntu 15.10 with
sudo do-release-upgrade
Everything worked fine. But when I tried to change the desktop background unity crashed. I restarted the computer and tried to change the desktop background again but the background didn't change.
Now when I try to move any windows, the dragged window leaves trail behind. This happens only when the window are dragged on desktop background.
But when I drag windows over other (maximized) windows there is no such problem.
What might have happened and how can I fix this?
EDIT: I have realized that this problem occurs only when rhythmbox is running. If I kill rhythmbox process using system monitor or not start it all then the problem doesn't occur.
Best Answer
I ran into this problem after upgrading from 15.04 to 15.10 via update manager.
I did not have rhythmbox running. I removed and reinstalled it, as well as all dependent packages, via the software center; those did nothing.
Scrolling through the system monitor, I noticed that Nemo was running. I killed it and the desktop refresh problem immediately stopped. I was, however, left with a black desktop background that did not display my wallpaper. The instructions in this answer worked for me:
I'm not sure what the underlying cause of these problems is, but I hope this answer will at least help people work around it.