Ubuntu 12.04/Gnome 3 - Repair or Reinstall
I don't have anything specific at this time. However, as a "newbie" and messing around with various settings/configurations can really mess things up. And, sometimes, files and such may get corrupted and, as such, rather than attempting to determine exactly what is messed up; like with Windows, it is sometimes best to just perform a "repair" or at worst do a "clean" install and just start over anew.
One thing I have not done with Ubuntu is perform a "full system" backup periodically. I use Acronis True Image with my Windows system. I am not familiar with the backup tools for Ubuntu (yet).
Anyway, thanks for the response.