We had this plugin working until recently, when I upgraded the site to 3.5.1 and updated all plugins.
Now, no comments show up and there is no comment box. When I reactivated the plugin, we got an emamil saying:
Thanks for trying out Facebook Comments for WordPress!
We just thought you'd like to know that your current XID is: .
There was no value for the XID. I had gotten the appID from my developers.facebook.com account, so I'm not sure if this XID was the same thing. In any case, it's not working.