Well, again without prior notice to its users the MSN Messenger service has been up and down all day. Many users have complained that they are un-able to sign in and when it IS possible to sign in, a couple of minutes later you are knocked off again!
I looked around Microsoft and MSN (again) for more information on this outage and could find none. Lets hope its not the same as the last time where it took almost 4 days to restore service to the majority of its users.
So if you cannot sign in right now, dont worry 1000"s of others have the same problem too ;)