I'm running Ubuntu 12.04 LTS on VM. It was fine till last friday. There were some updates available, some were related to security stuff, I don't remember exactly. After that my system is broken. I can't login with my regular user. Only guest login works. I went to recovery, after that I tried some instructions from, Getting an "Authentication token manipulation" error when trying to change my user password
Although I couldn't reset password of due to error "Authentication token manipulation Error", atleast I could login back with my regular user. But sudo stopped working, invalid password. I tried pkexec, which also fails with authentication error.
Could somebody please help? Otherwise I may have to reinstall the OS.
Thanks in advance, psk