I'm not sure this is a JFBConnect issue. I went to your site and was unable to use the JomSocial registration form normally (without logging in using a social network). When I click the Register button, the following Javascript errors showed up in the browser console:
Uncaught SyntaxError: Unexpected token < ajax_1.5.pack.js:1
An invalid form control with name='cmc_groups[EMAIL]' is not focusable. index.php?option=com_community&view=register&Itemid=162&lang=es:1
An invalid form control with name='cmc_groups[FNAME]' is not focusable. index.php?option=com_community&view=register&Itemid=162&lang=es:1
An invalid form control with name='cmc_groups[LNAME]' is not focusable. index.php?option=com_community&view=register&Itemid=162&lang=es:1
I'm not sure what those fields are (they seem different than normal JomSocial fields) or what's causing the errors. It could be JomSocial or another 3rd party extension, but I don't think it's JFBConnect.
If there's some reason you think our extension is causing the problem, or need anything else from us, just let me know.
Thanks,
Alex