[ubuntu] can't login through desktop GUI after upgrade from ubuntu 10.04 to 12.01 desktop

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http://ubuntuforums.org – Dear Sir/Madam, I have just upgraded ubuntu 10.04 32 bits desktop to ubuntu 12.04 32 bits desktop (through login into ubuntu 10.04 desktop GUI screen, and then upgrade to 12.01 through the popup "update manager" GUI screen), but got can't login though GUI screen problem, i.e. when login through the GUI screen with the correct password, after a few seconds, it is back to the same GUI login screen again. However, it can login in through terminal. Have spent sometime on googling and trying to resolve the problem, but unsucessful (during this period of time, run command tasksel sev (Hardware)