ipAuthenticator detects my IP address as 127.0.0.1. I believe this is because I run on a Pressflow on a Mercury server, which means there is Varnish acting as a proxy. This problem might crop up with other proxies as well.

To fix this, do not rely just on $_SERVER['REMOTE_ADDR']. Using ip_address() (http://api.drupal.org/api/drupal/includes--bootstrap.inc/function/ip_add...) instead will probably solve this problem.