OK, so I am now on my 6th fresh format and install of Ubuntu 12.04 (in under a month). I installed gnome shell, gnome desktop, and tweak tool. For whatever reason I cannot select _shell user-theme" because there is an orange triangle next to it which when I hover over it I get "shell user-theme extension not enabled". How do I fix this? Is there a way to determine what version of gnome shell I am using so that I don't break this again with unmet dependencies? Where is the best place to look or even begin to fix this? Thanks in advance for any and all help.