Signing in to MSN Messenger failed because the service is temporarily unavailable. Please try again later. 81000314

you can check the msn server status here http://messenger.msn.com/Status.aspx

This error does not relate to a connectivity or client misconigfuration error. It is an MSN server error. MSN hosts different MSN/Hotmail accounts on different servers and sometimes performs maintenance on individual servers thus causing this error whilst allowing other separate accounts to connect.

The error seems to relate to a DNS error with the MSN server.
An apparrent solution is to:
Add the following to entries to your hosts file:

65.54.239.80 messenger.hotmail.com
65.54.239.80 dp.msnmessenger.akadns.net