http://forum.ait-pro.com/forums/topic/login-security-login-monitoring-read-me-first/#post-9030
If you have a custom login page that is hooking into the normal WordPress login process. Example: The Form Action is pointing to action=wp-login.php, then no matter where the custom login page is it should still be processed successfully, but if you are doing additional things that do not allow normal/standard login form processing then these things would be what is preventing login form processing.
Are you using another Login plugin or have you created the custom login page yourself? If you are using a Login plugin then please post the name of that plugin.