Quote Originally Posted by klaus2008 View Post
Two suggestions:

1) (Re-) start compiz with the menu entry from the "Preferences" menu

2) Restart the Xserver with the Ctrl-Alt-Backspace key combination
I get this problem every now and then. For my case, restart compiz does not fix the problem. Re-start Xserver can fix the problem but it's a little more painful. I always managed to fix the problem by doing this at any terminal windows :-

Code:
   $ gtk-window-decorator --replace &
I don't know why gtk-window-decorator misbehaved for my case. It is still running but it just misbehaved, so restarting compiz fixes nothing. If 'gtk-window-decorator' has died, then restarting compiz will fix the problem.