Many problems have plagued the inbox, try the following temporary fixes: Clear cache, uninstall and re-install the game, lastly switch browser. RocketMelt, Flock, SeaMonkey, Opera, Maxthon 3, Safari, FireFox, Internet Explorer, Avant Browser, K-Melon, Comodo Dragon, and Google Chrome are just a few browsers you can try. I am sure the developers are working very hard to fix them for all of us.
You may also want to check your flash player.
‎1) Remove the game from FB.
2) Log out your FB
3) Clear cookies from your browser.
4) Download http://get.adobe.com/flashplayer/?no_redirect
5) Close your computer and open it again.
6) Re-Install the game.