All I can guess is that your Application is not setup correctly. Please go to the Autotune -> Facebook App area in JFBConnect and click the "Refresh" button in the top menu bar. Then, make sure that all of the settings are at their recommended values.
For that issue specifically make sure the Domains and Site URL settings are correct. If they don't match the URLs of your site, that would be why you're getting that error.
I hope that helps,
Alex
Unauthorized URL at Facebook
