Most of the questions are better put on the facebook connect and developer forums.
One thing to make sure works is if you use xd_receiver.htm file for fb communication, make sure it's not blocked as in rewrite rules doesn't work. So open the url in your browser to make sure it is not served by eZ Publish (if it's not working you'll get an error page from your own site instead of the html in the xd_reciver file)