Both Ubuntu versions 12.04 and 12.10 use the nautilus 3.4.2. Therefore this (nautilus 3.6.1) can be considered as an "unsupported" version.
My suggestion is to fill a bug against nautilus 3.6.1 in gnome bugzilla.
Edited this answer according to new info in the comments.
Other time, reconsider twice before you add an external and unsupported PPA in you Ubuntu system,
It can brake your system in a blink of an eye. (as did in this case).
Some PPAs updates-upgrades essential system packages and this can result in a very frustrating experience.
To solve your problem open a terminal and remove the ppa with bellow commands
sudo apt-get install ppa-purge
sudo ppa-purge ppa:gnome3-team/gnome3
sudo apt-get update
sudo apt-get dist-upgrade