Are you using CB Connect with Redirect instead of popup? How big is the popup window? It should be quite small so that shouldn't be an issue. Additionally it's just a "heads up" to the developer account and should have no negative impact on the usage; normal users will not see that. Please ensure you've configured Facebook and CB Connect as instructed in the below tutorial.
www.joomlapolis.com/support/tutorials/99-plugins/18364-cb-connect-how-to-configure-facebook
Be sure to enable debug mode and maximum error reporting in Joomla global configuration during testing so errors can be displayed.