If the password contains '&' you get the following error:
Warning: ldap_bind(): Unable to bind to server: Invalid credentials in usersc/plugins/ldap_login/hooks/loginFail_body.php on line 49
This appears to be a known issue with the ldap_bind function. I could only make it work using html_entity_decode on the password as suggested here: https://stackoverflow.com/questions/12858493/php-ldap-bind-fails-when-password-contains-ampersand