I haven't seen any posts with this problem so I thought maybe this might be a heads-up.
My Nadia 64bit version was working fine, then along came an update for Intel video. I upgraded with no problem. However later on my system would just log me off for no apparent reason. At first I thought it was a fluke, but it kept it up.
I Googled for a method to downgrade to previous video driver and followed the instructions and now my system is back to normal.
The following page gave instructions on how to downgrade:
http://www.hecticgeek.com/2012/08/insta ... rs-ubuntu/
I then did the following:
apt-get install xserver-xorg-video-intel=2:2.20.18~quantal~ppa1
This method worked for me.