Failed to receive a reply from the session manager

The subject is the message I get after I have clicked on 'Logout' and then 'shutdown'. When the shutdown doesn't happen I go back and click on 'logout' again. That is when the message shows up. That message is followed by "session manager must be in idle state when requesting a shutdown". If I wait long enough #! does indeed shutdown. Why am I getting this message and how do I stop it?