If a user registers 'normally' with Joomla, then they will follow the Activation settings you've configured in the User Manager -> Options area. It sounds like you have it configured for Admin or Self (Email) activation, which is why the user isn't activated.
JFBConnect has an option to 'Skip Joomla Activation', which allows social network users to not have to activate themselves, while users registering the old fashioned way have to authenticate their email (or be approved by an admin).
JFBConnect doesn't change your activation settings in Joomla, so I'm not sure how that would have changed, but hopefully that helps get you going.
Thanks,
Alex