I've discovered an annoying bug of light-locker: if a vnc-server (x11vnc for example) is installed and set up, every time you choose to lock your session up (no matter physically or via a vnc), it greets you with a black screen. As a remedy, you have to either restart lightdm service or reboot the machine.
Needless to say, removing light-locker resolves the question. But... As there's no a locker anymore, I need a new one.
I tried Xcreensaver and Gnome-screensaver. Both of them install nicely, but the log out button doesn't seem to work. How do I fix it?