windows messenger wont allow contacts that have previosly been blo

hi i added a user to the "block" list in windows messenger and when i try to
add them back to the "allow" list it doesnt work,i added them to allow and
hit "OK" and then when i bring it up again theyre right back on my "block"
list or when i right-click on the contact and click "unblock" or click
unblock from inside the conversation window nothing happens.does anyone know
whats wrong?is it a temporary problem with their servers or what?thank you.