There is some other extension that is inserting the following script onto your page and it is conflicting with the newer version of the Facebook Javascript library that JFBConnect includes. This is a timing issue based on which one loads first, which is why it will sometimes work and sometimes not. This script needs to be removed for it to work properly.
<script type='text/javascript'>
// Load the SDK Asynchronously
(function(d){
var js, id = 'facebook-jssdk'; if (d.getElementById(id)) {return;}
js = d.createElement('script'); js.id = id; js.async = true;
js.src = '//connect.facebook.net/en_GB/all.js';
d.getElementsByTagName('head')[0].appendChild(js);
}(document));
</script>
All of a sudden the Facebook box dissapeared in the hover box...
