Ubuntu 12.04 : Login screen re-appears even after providing right credentials..

In today's ride on my desktop- I found this issue.. which is so new to me.. My Ubuntu 12.04 is showing login screen again and again even after giving correct username/password..

By digging the logs, These lines from /var/log/auth.log gave some clues..

Aug 19 13:02:00 desktop lightdm: pam_ck_connector(lightdm:session): nox11 mode, ignoring PAM_TTY :0
Aug 19 13:02:01 desktop lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "shivaram"
Aug 19 13:02:01 desktop dbus[901]: [system] Rejected send message, 2 matched rules; type="method_call", sender=":1.23" (uid=104 pid=1582 comm="/usr/lib/indicator-datetime/indicator-datetime-ser") interface="org.freedesktop.DBus.Properties" member="GetAll" error name="(unset)" requested_reply="0" destination=":1.13" (uid=0 pid=1257 comm="/usr/sbin/console-kit-daemon --no-daemon ")
Aug 19 13:02:06 desktop lightdm: pam_unix(lightdm:session): session closed for user lightdm

Here:

• lightdm is the default Display Manager that's provided by Ubuntu 12.04.. 
• shivaram is the username.

These steps resolved the issue..

1. Press Alt+Ctrl+F1  to get a terminal i.e tty1
2. login with your credentials.
3. execute the below command by replacing your username.
   

   sudo chown yourusername:yourusername ~/.Xauthority

     4. Now press Alt+Ctrl+F8 to get back to graphical interface

.Xauthority file takes care of authentication for X Windows or simply GUI. By changing the owners of the file, we can get authenticated.

And now, my graphical session is letting me inn.. :)