This looks to be completely a Facebook issue. Since it's happening on Facebook's own demonstration page, which has nothing to do with JFBConnect, that means it's on their end. There's nothing we can do to get around a bug that's within Facebook itself.
A bug was just reported earlier today by another Facebook user:
developers.facebook.com/bugs/228391867266935
If you're experiencing this issue, we recommend you use the "Does this repro describe your issue?" link and give information about your page.
Hope that helps. This issue isn't affecting everyone, and we haven't been able to determine what's common between the sites that have the problem. Hopefully, the bug report form above will help Facebook narrow down the cause or get a common solution.
Thanks,
Alex