Jean Claude,
Thanks for the PM. I never accessed the admin area and just did some more sleuthing. The issue on your site seems to be coming from your language switcher at the bottom of that page. I'm assuming that module only shows up in the onyx template.
The issue is that the following code is being inserted on the page:
if(top.location!=self.location)top.location=self.location;
That code is checking if the current page is inside a iFrame, and if so, it's reloading the page 'out' of the iFrame. All apps on Facebook are loaded in an iFrame, so you'll need to remove that code.
Hope that's all it takes!
Finally, please consider leaving a rating and review on the Joomla Extension Directory for JFBConnect, or our support. It's certainly not required, but very appreciated!
extensions.joomla.org/extensions/social-...ook-integration/7215
Thanks,
Alex