Simon,
While we still do support some issues with JFBConnect v4.1.2, we're highly recommending all users move to v4.2.0. If you're still having issues with 4.1 that you'd want fixed, instead, we'd recommend moving back to 4.2 and continuing to work on a fix for the email issue.
When you upgrade to 4.2, you may run into some issues since our extensions were not meant to be downgraded. The database tables that were updated when you moved to 4.2 will not get reverted.. so when you install/upgrade again, you may get MySQL errors, just so you know.
When you're back on 4.2, if you're ok with it, can you send me both admin credentials for Joomla and the Facebook login information for a user that is seeing the email field? With that, we should be able to narrow down the issue and fix it quickly. As it is now, we simply can't reproduce the problem.
You can Private Message me by clicking the arrow under my picture (<----) and hitting the mail icon.
Thanks,
Alex