The Facebook comments won't update the "Be the first to comment" line in your extension. The commenting feature built into 3rd party extensions would need to be aware of the Facebook comments block, and I'm not aware of any that do that.
I'd recommend disabling the comment feature of your blog extension.
I hope that helps, but if not, please let me know what version of JFBConnect you're using. Also, please post from the account you subscribed to JFBConnect from. Priority support is for active subscribers only.
Thanks,
Alex