Unity ,gnome-shell ,cinnamon what ever not working

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http://askubuntu.com – using Ubuntu 12.04 . First it came with Unity , then with a zeal of trying other Desktop Environments and i have installed gnome-shell and no conflicts , works fine.Then i have gone through Lubuntu and Xubuntu as usually . But some panel problem started with Lubuntu raised and i have removed Lubuntu DE from my PC . but that thing got conflicted with my Unity , Gnome and Cinnamon & they are not working . these three are not having only of their Panels . I just see any empty desktop . Currently only KDE and XFCE can run fine with my Ubuntu 12.04.But i want to back with Unity , Gnome and cinn (HowTos)