Problem with Gnome3 on Ubuntu

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http://askubuntu.com – I recently installed the gnome3 on my Ubuntu some 1-2 months ago, it was working nice, but today, i was trying a theme, and then after reverting, the gnome-shell is not working!, When i select gnome, it runs the ubuntu-2d or something mixed, there are no animations, but it is not ubuntu-2d,whatever it is... is no gnome! Reinstalled gnome-shell, gnome-core, gnome-session! Now the "gnome" is not installing, it says that i do not have gnome-core installed, or when clicked "Install", It does nothing, but within half a second, switches between Installing.. and then back to "Free" . What s (HowTos)