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