Philip,
I just got into your site to debug things, and found the problem. There's a field configured in Community Builder called "cb_myvstore". When that field is enabled, and JFBConnect tries to save the user, it throws the following error:
Unknown column 'cb_myvstore' in 'field list' SQL=INSERT INTO ...
When I unpublish that field in CB< everything works normally (from what I can see).
Can you let me know anything about that field? Also, is it configured correctly, however you configure it, and is it a field you absolutely need for your site?
Hopefully, that will get us started on finding a solution. Even if required, we should be able to find a way to make JFBConnect work with that field.. but again, we'll just need to know a little more how it's purpose and how it's setup.
Finally, I installed 2 file manager extensions on your site, which you're free to uninstall: extPlorer (which I couldn't use as I needed to be a Super Administrator) and OSE Fileman (which I used to do the debugging above).
Thanks,
Alex