Esteban,
On your page (inside the lower frame), I'm not seeing the inclusion of the Facebook Javascript API. In the HTML, there should be a reference to all.js right after the body tag, but I'm not seeing it. This is inserted by enabling the JFBConnect - System plugin.
If that is published, let us know, and we can look further, but it's strange that that's not showing. If you have caching or anything else enabled on your site, you may want to disable it for testing purposes right now too.
Thanks,
Alex