Due to problems related to updater files on MAC. Unblocking Contacts function doesnt seem to work on Windows Live Messenger 2009. Despite trying once and again, the contact remains blocked, and even if you go to the blocked contact list under Tool, they are not there. If you check with online IM like Meebo they are actually unblocked. Read the article to know how to make the unblock function work on Windows Live Mesenger 2009.