Richard,
I'm very, very sorry for the delayed response. We'll be all over this issue going forward to get you going.
I just looked through a few different pages, and the HTML looks right.. no obvious problems. It took me a minute to find the JFBCLogin Module. When I tried to login, I got to a 500 error page when trying to load something from JFBConnect.
Can you try a few things:
1) If you have any profile plugins installed, make sure that the corresponding component actually installed too. (Don't enable the K2 profile plugin if you don't have K2).
2) I'm assuming you're integrating with JomSocial. Please try disabling that (or any other profile plugins) temporarily, and see if you still get the error.
3) If it goes away (my guess is it will), try re-enabling the JomSocial profile plugin and disabling the avatar import - this has caused problems in the past.
4) If the above doesn't work, please try forcing all the permission requests in the "Permissions" tab. Right now, it seems like the email and post to wall permission are required, but data permissions for profile integration are optional. This requires an extra request to Facebook, and could be the problem.
Hope that gets you started. Obviously, none of the above should be required, so if you have to disable something, let us know.. and we'll figure out how to re-enable it.. but first we need to narrow things down.
Again, sorry for the delay, but we'll get you going,
Alex