Lili,
Sorry for the delay.
There's 2 issues on your site that I see:
1) In JFBConnect, you've specified a language of "fr". This is not a valid language string. It looks like it should be fr_CA. Or, you should just leave that parameter blank and JFBConnect will automatically detect the language to use.
2) There's another extension installed on your site that integrates with Facebook. This will conflict with JFBConnect once you fix #1 above. Other Facebook extensions are fine, but they can't re-include the Facebook Javascript library, which the one on your site is. If you open the HTML and search for "all.js", the 2nd block at the very bottom is the one that needs to be removed. Most extensions that have Facebook integration have a way to disable it, and you should do that to get things going.
Hope that helps, and good luck,
Alex