Inbox errors - Temporary fixes
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.