I've just upgraded to 16.04LTS. During installation everything froze. After an hour "frozen" I restarted the Laptop. I would get caught in an endless loop of turning on and off the screen. I went into recovery mode, connected manually to WiFi, ran the dpkg repair command, apt update and Upgrade -f. After that I was able to properly boot. After logging into my Account, though, only the background changes and except for the mouse pointer and desktop background (it's the correct background and even correctly changing) I have no GUI. Service lightdm restart only brings me back to the login-screen. Any suggestions?