I'm running ubuntu 12.10 x64 and sometimes when I update my system after it restarts my laucher and everything is gone. I have just the desktop background. in order to get everything back I need to do
sudo apt-get install linux-headers-$(uname -r)
sudo restart lightdm
I'm running a GTX 670 I don't know if that has anything to do with it but does anyone else have this problem? like I said its not after every update. It seems very sporadic.