All of a sudden i am unable to login into my user account. I have activated root account and i am able to login into that root account, however i cant able to login into my user account. I am very sure it is not a password error. When i login into my user account the screen flickers and again it is showing the login screen. Some times a popup appears in the top right corner as you see below. Can anyone help me to solve this problem ? i have posted this same question in ubuntuforums also but still no solutions helped me. I hope someone here will solve this issue.