Unable to Login to ubuntu after installation of Gnome desktop

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http://askubuntu.com – After installation of gnome desktop on my ubuntu 12.x LTS, i'm unable to login to my administrator account. Please note that using guest account i've removed gnome desktop and killed gnome session but i'm unable to run any other sudo command from my guest account. The error is /var/lib/dpkg/lock cant be unlocked. Request help. Regards Utpal (HowTos)