
Use webmessenger until we figure out how to solve it.
http://webmessenger.msn.com or http://iloveim.com
Check also MSN Service status: http://status.messenger.msn.com/Status.aspx

Update: It seems the service is returning to normal. I would suggest signing out and back in again if you are still receiving the error. Apparently engineers investigated the problem and found a fix.
If none of these methods listed above won't work, we recommend you to run registry fix tool.