No panels or menus after upgrading to 14.04

Solution 1:

I tried reproducing your trouble by disabling Unity-plugin, after this resetting Unity or its settings didn't work. So, this what I've done trying to get it back:

install Compiz Config Settings Manager if you don't have it:

sudo apt-get install compizconfig-settings-manager

Now, you have to go to Compiz Config Settings Manager and enable Unity-plugin when Compiz manager opened navigate to Unity-plugin or just type in search Unity then click on it and on the left put a tick wait a sec it should get back.

How to get to Compiz Manager and Terminal without Unity interface when nothing's responding even pressing Ctrl+Alt+T ? There's always the way to get around, for example press Ctrl+Alt+Del you'll get System Monitor navigate to File Systems you'll get listed with your HDD subsections and simply click twice on Home section now you should get Nautilus running. Navigate to / and hit the search bar just type Terminal now you can launch Terminal from search result, the same way type CompizConfig and you should get Compiz Manager launcher.

What other ways you can try using Terminal try to purge Unity:

sudo apt-get remove --purge unity

Now reinstall it along with ubuntu-desktop simply type and run:

sudo apt-get update

sudo apt-get install --reinstall ubuntu-desktop

This should automatically install and put Unity back on, you'll be able to see the packages that are going to be installed, if not run:

sudo apt-get install unity

After all may require reboot, didn't occur to me.

if you want or need to reset Unity on Ubuntu 14.04 you can use Unity Tweak Tool to do so, if you don't have it installed:

sudo apt-get install unity-tweak-tool

and to reset run:

unity-tweak-tool --reset-unity

Alternatives, all this stuff I wrote should definately work if everything else is fine including video drivers and you can try it in addition with Gnome for example, simply install gnome-shell:

sudo apt-get install gnome-shell

now reboot, and then at the login screen choose gnome-shell and log in, if everything is ok, it should work 100%, if not, the problem is not only in Unity, it might refer to video drivers issues as well.

These are all ways that I could figure out, so good luck!