Comment 18 for bug 463915

Swajime, I don't know if this will get back the UNR desktop back, but you can get the default desktop by renaming the directories .gnome and .gnome2 as .gnome_old and .gnome2_old
Then, log back into your desktop, and gnome will use the built-in defaults to make the .gnome and .gnome2 directories. If everything works as expected, you can then get rid of .gnome_old and .gnome2_old. If not, you can always move those directories back to their original names and log back in to get your (albeit broken) desktop again.