Some time ago, I helped a colleague install Ubuntu in a Sony Vaio, which ended up having SSD problems. Today, his computer started without the bar and menu from Unity. Only the desktop and icons were appearing, and the keyboards shortcuts were also not working.
To fix, I found this askubuntu question, that worked like a charm.
The steps were simply:
1 - Enter the terminal mode with Ctrl+Shift+F2 (or other number); 2 - Login; 3 - Enter the commands
export DISPLAY=:0 sudo dconf reset -f /org/compiz/ setsid unity
4 - Reboot with
5 - Verify everything is working now.
This was enough to fix it.