title: Game center log in issue
body: <p>I have a strange issue with Game Center and I hope someone can help me. My expected behaviour is this one. I'm on iOS 6 and in debug:</p>
  
  <p>-When I start the application I log with GameCenter but if the user is not loged I don't show the interface, my idea here if it's logged to GC fine but if he is not I don't care</p>
  
  <p>-After inside the application I have a button to log on gameCenter if he wants to acces to features related to that</p>
  
  <p>The problem comes that when I try the app with a device that has never used my game, even if he is logged to gameCenter, the user is not authenticated, if he logs from my button with the interface the next executions he is loged at the start without interaction</p>
  
  <p>The strange thing is that inside the completion handler the <code>NSError* error</code> param is nul but local <code>localPlayer.isAuthenticated</code> is false</p>
  
  <p>How that's possible? Anyone has found this issue?</p>