I have attached the Xorg.0.log file. (in odt as log files are not allowed)
Thanks for replying Adfeno.. :)I searched Xauthority on web and found a thread with similar problem and solution..
https://askubuntu.com/questions/300682/what-represent-xauthority-fileThe solution could be relevant as i used to use sudo nautilus quite often (in order to get rights to edit files on my external HDD)
Please share your comments on it.