Why do I keep getting the "You have 1 invitation." notification on Windows Live Messenger?

This is what I mean by the “You have 1 invitation.” notification: http://i93.photobucket.com/albums/l64/deadsy__x/msn.jpg

I have clicked on it and I’ve ignored the invitation but that notification keeps on coming even after I sign out of my MSN. When I sign back in I see that notification and when I click on it there’s no invite. Everytime I click on the [x] to close the notification but it just keeps on coming back even there is no invite.

So how do I fix this problem? I’ve tried repairing the msn messenger but it still won’t go away. What is going on with it? How do I fix it?