Network manager in disabled state for Ubuntu 10.04.3

Suddenly if your network manger has gone to disabled state in your Ubuntu 10.04.3 and you are not able to enable it or make any changes even after restarting, you can do the following to fix the problem:

rm -fv /var/lib/NetworkManager/NetworkManager.state

service network-manager start

reboot

This will re-enable network manger.