Not able to login via GUI : Error in locking Xauthority file

1. Switch to command line "Ctrl" + "Alt" + "F6″

2. enter login, provide user name and password

3. type startx

   it should switch to GUI mode

but if you get Error in locking Xauthority file, try following:

The error i got means i do not have authorize to access $HOME/.Xauthority file in my user directory.

If you have the same problem, simply run chown as root to change the ownership back to the user. At the terminal as root, go to /home/user
# cd /home/user

list all files with ownership
# ls -a -lh

change file/files ownership to your user
# chown user:user .Xau*

reboot the machine, everything should be working as normal now.

Source: http://namhuy.net/1077/fixing-error-in-locking-authority-file-xauthority.html