First i thought that I forgot the password literally, then i went to the system recovery to change the password. After changing the password the same thing is happening i.e. It is showing incorrect password. I tried logging in by pressing Ctrl+Alt+F2 and it is logging in from there but when i come back by pressing Ctrl+Alt+F7 again the same thing is happening. I even tried using the older versions of Kernel but the same issue is happening again. Somebody help.