failed to load session "gnome" after Precise Pangolin update

[Carla Sella]

I have Precise Pangolin Beta 1 installed on this hardware:
http://wiki.ubuntu-it.org/CarlaSella/lshw
Yesterday after launching apt-get update, apt-get upgrade and apt-get dist-upgrade after rebooting I get this message after inserting my password:
"failed to load session "gnome""
If I logon as guest there is no problem, this happens only logging on to the only account I have, my account.
As I have root on one partition and /home on another, I tried reinstalling Precise Pangolin Beta 1 on the root partition from a USB key created form the iso of 01/03/2012.
As soon as Precise is installed I can logon to my account but if I launch updates again with: apt-get upgrade and apt-get dist-upgrade I get the same exact problem after rebootin.
So now I am locked out form my account.

[Carla Sella (carla-sella)]

I had this problem yesterday, this evening I turned on my PC, logged into a terminal session (ctrl + alt + F1) launched a apt-get update, apt-get upgrade and rebooted, now I do not have the problem anymore.