Actually I just found out that the problem is not related to the second user because I locked my session, pressed "Change User" in the locked screen, took me to GDM and it restarted GDM while killing my session. I've also noticed that there were two GDM instances running in tty9 and tty10, at least after that "restart".
I had previously enabled debug on GDM so I'm attaching the syslog. For comparison with the syslog file, here's the time when auth.log registered my session closing: Jul 8 01:37:06 ubuntu-desktop gdm[5836]: pam_unix(gdm:session): session closed for user firstuser ** Attachment added: "syslog" http://launchpadlibrarian.net/15883172/syslog -- Multiple users login crash https://bugs.launchpad.net/bugs/244737 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs