I am tweaking my new install of Kali 1.0.6 32 bit and have a problem the window manager crashing when you lock the screen. I have xfce4 installed as the default window manager with xfce4-panel 4.8.6. I have added Action Buttons to the panel but when I choose Lock Screen from Action Buttons the screen goes black and keeps flickering endlessly. Moving the mouse or pressing a key does not change anything. I can get to tty1 via ctl-alt-f1 and reboot, but that's about it. Is there a command to restart the window manager? How can I resolve this?