This could be like some problem that you've added the maximum contacts to your allow list. Not your contact list, your allow list. Tools> Options> Privacy. You can try noroom's list cleaner. Here's a link with all the things it does and a download link is provided at the bottom of the page:
http://www.tsjaa.nl/modules.php?name=Software&op=viewarticle&artid=493
I hope that works for you, because all you might need is to simply clean your allow list up so you have space for contacts you'd like to talk to.
Edit: Also, the official site for the program:
http://noroom.msnfanatic.com/listmanager/
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