After I've upgraded from Ubuntu 13.04 to 13.10, I can no longer use the Session Indicator "Log Out..." menu.
As soon as I click on it, the screen goes blank with no mouse or keyboard input, so I cannot do anything other then pressing and holding the power button down to force the computer to shut down.
The same also happens if I enter the Terminal command sudo service lightdm restart
.
I can switch to Guest Session but then I have the same problem again when I switch back to my user session, the only difference: the screen is not black but simply my regular desktop screen is frozen.
Any ideas that can help me out will be much appreciated.