Here are my settings: https://www.dropbox.com/s/enhn2tscoc21gnw/Screenshot%202014-04-27%2013.59.52.png
I have define('FORCE_SSL_ADMIN', true);
in my wp-config.php, so the Meta widget tries to link to the mapped login page with https in front, which doesn't work. However, even if I go to the mapped login page without https in front, it redirects to the mapped login page with https in front, which again doesn't work (because there's no SSL certificate for the mapped domain).