I got the same problem. But now it is working fine after disabling guest account as mentioned in the below article
https://askubuntu.com/questions/62564/how-do-i-disable-the-guest-session -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1733557 Title: Login screen showing Authentication Failure Switch to greeter... To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1733557/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
