Thank you, Google Translate

Invalid Argument
The destination URL of the cross-domain of Facebook Connect (http://xxxxxxx.it/index.php?option=com_ .... 087% 22% 7D) must provide the URL of the callback (http : / / www.xxxxxxxx.it) as a prefix. The callback URL can be configured in settings.
Is it possible that it's complaining because one of the URL's has www. and the other does not? On my page, this is the javascript that JFBConnect produces:
FB_RequireFeatures(["XFBML"],
function() {
FB.Facebook.init("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX", "index.php?option=com_jfbconnect&view=xdreceiver&format=raw");
});
So JFBConnect doesn't even specify the entire site URL in the prefix.
Are you going to <!-- m --><a class="postlink" href="
www.xxx.it/">
www.xxx.it/ or
xxx.it/">
xxx.it/ in your browser?
Do you have any SEF turned on that might be messing with the URL?
Thanks,
Willl