setValue() on a non-object in

That's not an error we've ever heard of before. Right now, I can't test on your site because your Facebook App is still in test mode. Even if it was live though, I'm assuming I'd just see the error you posted above... which doesn't nail things down too well.

From the line of code that is throwing the error, it seems like the standard Joomla user registration form that JFBConnect loads is not being read properly. Again, that's not something we've seen, but here's some steps I'd recommend:
1) Make sure you're running the latest version of Joomla, currently 3.4.3
2) Re-install JFBConnect v6.4.1. You don't need to uninstall first, just use the upload manager like it was new. That will refresh all the files, in case an issue happened during the original install.
3) Disable any Social Profile Plugins you have enabled.

Check/test each of those and let me know if any help. If not, please Private Message super admin credentials and we'll gladly investigate further. To PM me, just click the mail icon under my name to the left.

Thanks,
Alex