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Unfortunately, sometimes Unity Desktop (including launcher and dash) does not load. This is an existing painful bug in Unity for quite sometimes. Usually the reason for not loading is because Unity plug-in turned off automatically. There are few steps should be taken to resolve the problem.
The first thing you should do is to install compizconfig-settings-manager by running,
$ sudo apt-get install compizconfig-settings-manager
Afterwards, you need to run DISPLAY=:0 ccsm to lunch Compiz configuration. Try to find Unity plugin and enable it.
The last step is to reboot your machine and check the result.
If the problem has not resolved yet, only remaining solution is to install the entire Unity again by running,
$ sudo apt-get -f install && sudo apt-get --reinstall install unity
