I did an upgrade to 11.10 from 11.04
Installed LAMP server components and Libreoffice latest.
Suddenly when I tried shutting down system, it logs me off and takes me to the Login screen.

I went to terminal and tried
sudo shutdown 1
I got a prompt saying

System is shutting down for maintenance in 1 minute
But Nothing happened.

Finally I powered it off by switching off UPS.
I erased the installation and reinstalled fresh AMD64 version from ISO & pendrive. Still got the same problem.

Now sometimes PC shut-down normally, sometimes it takes me to login screen.

Any Solutions on this?

Thanks in advance.