If you enable “Desktop Cube” from CompizConfig settings manager, you are prompted to disable desktop wall and other plugins. Disabling these plugins might cause havoc to your Ubuntu system. Immediately after you click on “Disable Desktop Wall”, the launcher and the top bar will disappear from your Ubuntu. You will see no borders around windows, so you cannot close them, move them, or resize them. And worst of it all, hotkeys are also disabled. You cannot run terminal by pressing Ctrl-Alt-T. All you can see is the desktop background and the stuff on it. The problem would not be solved even if you restart your system. This might cause you to format your system and install a new copy of Ubuntu. But, there’s a simple solution to it.
Immediately after you disable desktop wall, you will no longer see the top bar. So, you cannot logout, restart or shutdown. So, Press Ctrl + Alt + F1. You will be taken to a console where you will be prompted to enter username and password(It will be better if you login as root user, since you need to use SUDO command.) After entering the necessary login information, type the following on the console:
sudo service gdm stop
sudo reboot
Your computer will now reboot. Once you get to the login window, choose your username and instead of logging in directly, look on the bottom. 
There’s a bar showing the language you are using and the type of ubuntu you are currently on. Click on the one saying “Ubuntu” and select “Ubuntu Classic(No effects)” from the drop down list. Now, enter your password to login. You should now see the top bar.On the top bar, click on Applications and look for “Terminal”. Open up the terminal and enter the following exactly as it is, on the terminal :
gconftool –recursive-unset /apps/compiz-1
gconftool –recursive-unset /apps/compizconfig-1
Remember that, immediately after “gconftool”, there is a space and then two hyphens (–) but there is only one hyphen after “recursive”. And there’s a space after “unset”.
That’s it. Now, Logout from the system. Again, on the login screen, select “Ubuntu” on the bottom bar instead of “Ubuntu Classic(No effects)”. Enter your password to login. You should now see the top bar, launcher and borders around windows. And the hotkeys should work too. Good Luck!
