1. We narrowed this down to the 'System - JSGCache' plugin. When disabled the registration, log out, relogging in and autologin worked for me. I didn't investigate the options within the plugin, but it's seems to be the culprit.
2. I disabled the 'Authentication - Facebook' plugin that is with your template. You should not use other Facebook authentication when using JFBConnect. This can cause unreliable behavior if different FB js libraries are included on the page.
3. I set the jQuery version in K2 to the same version that JFBConnect is using. The error on the console is now gone.
-Melissa