Occurring at randomly but at least every 30-60 minutes using different
Suddenly the screen becomes unresponsive: the mouse pointer moves normally, but
the windows do not respond to clicks, and gnome-shell does not work.
tty1 (ctrl+alt F1) works, but I have no local login and thus can do nothing
(using ltsp). Only Solution: To reset the system.
One thing: I found that if I start with session "gnome classic" instead of
"gnome 3" the problem does *not* occur.