That URL looks like you have an SEF extension that's altering our URLs. During the login process (which may be happening if you have the auto-login for Facebook enabled), the URLs JFBConnect uses should not be altered. Each social network is very picky that things don't change or they thing something 'bad' may be happening.
Please go into your SEF extension and have it 'skip' creating SEF URLs for JFBConnect.
I hope that helps, but if not or you need anything else, please let us know.
Thanks,
Alex