I updated from 13.10 from 14.04 a few weeks ago, and it was working fine.
But last night, after a login the wallpaper shows up, but the Unity does not,
and nothing else.
The weird thing is, that if I login as a Guest, it works 100%.
This answer didn't solve my issue, and it's for Ubuntu 13.04.
Best Answer
You could try to rename all directories containing configuration files and cache in your home directory - they should be newly generated after logging in again. I am quite sure that this will work, but ALL YOUR SETTINGS WILL BE LOST.
First, switch to the command line interface using
ctrl+alt+F1
and log in.Then rename all directories containing configuration files (do NOT delete them, just in case) using the following commands
After having done this you have to log out and back in. As this is not possible using the GUI you can run the following command:
This will restart the Xserver and you should be able to login. Unity should now work again, but all your settings are reset to their default values.