Most of the time when I log in, I after I enter my password, it says login in, and nothing else happens.
I have the same problem and found out, that there is already a confirmed bug reported on launchpad for this problem: https://bugs.launchpad.net/lightdm/+bug/986967
I wrote a question for this problem on askubuntu myself with a bunch of log output ... 12.04: LightDM freezes while "Logging in..." - maybe due to deactivated login sound
maybe it's an authentication problem, because when I can login, this line in auth.log is present:
polkitd(authority=local): Registered Authentication Agent for unix-session:/org/freedesktop/ConsoleKit/Session2 (system bus name :1.47 [/usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1], object path /org/gnome/PolicyKit1/AuthenticationAgent, locale de_DE.UTF-8)
and when I have the problem, this line isn't there...
(I somehow can't comment so I wrote an answer... I hope that isn't rude or something)
edit: There is an unofficial bugfix posted in launchpad. I didn't try it yet.
Michael Terry (mterry) wrote 6 minutes ago:
Hello! I think I have a fix for this. See https://code.launchpad.net/~mterry/unity-greeter/986967/+merge/104622 for the techy explanation of why this happens.
But if you want to test the fix or just are interested in fixing it soon, please try this ppa: https://launchpad.net/~mterry/+archive/ppa2
edit: People in Launchpad report that the bugfix is working, and that the problem may be caused by deactivating the login sound with Ubuntu Tweak. Maybe reactivating the login sound might fix this problem too until a official update is available