EDIT: This "trick" had a funny side effect: When I launched LXDE next time after this hard shutdown quite a few things had changed: All windows started without title bar and located in the upper left area so that everything else was covered, and, to make it even worse, Ctrl+. didn't work any longer so that I couldn't move those windows away from that position Fortunately, everything was back to normal after a shutdown and restart of LXDE.