I have just run a full Ubuntu software update on my Lenovo Thinkpad 2013. I now have no Launcher and no way of accessing applications, only an empty desktop.
2 Answers
Try to switch to a shell in character mode by issuing Alt-Ctl-F2, log in and issue this command unity
When you sign on you need to select the same Desktop you upgraded from. If you select the wrong one you can end up with a purplish screen and a movable mouse cursor.
To select the right Desktop click the gear icon next to the Sign In button on the login screen. This drop down menu will appear: