Contrary to what we posted earlier, the access that was granted to non-invited users over the weekend was merely caused by a server glitch that has now been fixed. That's the bad news for all of you out there who have not managed to get on the beta yet.
Here is the good news. We have the link for anyone who wishes to participate in the Windows Live Messenger Beta program to sign up. This link will take you directly to the Invitation Acceptance page that you would reach if you had been invited by another participant. So, if you are still on the outside looking in, jump in and get your Windows Live Messenger goodness!