Today I updated Ubuntu 12.04 with the Update Manager as usual. After that I restarted the system as required. When I logged in again the sidebar has only the trash can, the dash button and the switch workspaces button. No other shortcuts appear at all. The top bar is there but has nothing. Not even the power symbol. Finally on the desktop no icons appear, right clicking does nothing and using Ctr+Alt+T doesn't bring up the console. I restarted the computer several times and it's always the same. Help?
I solved it. I pressed Ctrl+Alt+F1 to enter the terminal. Then I used the last tip in this video and it worked i.e. I typed
sudo setsid service lightdm restart