The code on your logon page doesn't match the code you sent in the earlier post. You don't have the lines:
$Authenticate->addFilter("Username", "=", "s", "".((isset($_POST["Username"]))?$_POST["Username"]:"") ."");
$Authenticate->addFilter("Password", "=", "s", "".((isset($_POST["Password"]))?$_POST["Password"]:"") ."");
Those are necessary to force correct entries in the username and password fields before the login is accepted.