Problem to log after the last update of Ubuntu 12.04 LTS

I'm using a Ubuntu 12.04 LTS.

Yesterday I did an update of the system. Now I cannot open either the graphical part or the console (Alt+Maj+F1). On the console, when I tape the password, the system is freezing, same with the graphical interface.

Surprisingly, I can connect to the guest session.

I restart the computer and go the grub option to open the old version (3.12.0-65) and the system is working fine.

I want to inform you that the 3.12.0-66 has a problem to log on a session.

Is someone can give me the process to ask Grub to launch the 3.12.0-65 automatically instead of the 3.12.0-66.

You have this problem because you enabled proposed software source.

Kernel 3.13.0-66 is in proposed repository and is not stable.

I recommend to disable proposed in System Settings to avoid this kind of problems.

proposed is for testing purposes, not for normal use.