I'm not sure how I went about it but somehow I have managed to disrupt the "leave" and shutdown functionality of my system running 11.1

If I right click and select leave, the screen goes grey and just sits there. If I click the mouse(either button) or press a key the screen returns to normal but without any dialog. I don't get the usual prompt for shutdown, switch user, ....

If I press the power button, the same thing happens. I get a greyscale screen and it just hangs. Everything else seems to work normally so i'm not sure how to fix this. Any suggestions would be welcome.

Thanks, Dan