Okay, guys, i have this problem and i may need professional help; it appears smb4k made my /etc/sudoers file writable (according to log), hence, any sudo command will coerce this error:
ubuntu@ubuntu~$ sudo any 
sudo: /etc/sudoers is mode 0640, should be 0440
sudo: no valid sudoers sources found, quitting
i wanted to boot into recovery console and chmod 0440 /etc/sudoers, but it's a live system - it doesn't have a recovery mode. (more here: http://ubuntuforums.org/showthread.php?t=1695680 )

How would i mount the live system from another liveCD?