When I add the following js to any page that has a form. The submit button on the on-page form doesn't function.

What could the issue be with the code below?

(function($) {

    var $formLogin = $('#login-form');
    var $formRegister = $('#register-form');
    var $divForms = $('#div-forms');
    var $modalAnimateTime = 300;
    var $msgAnimateTime = 150;
    var $msgShowTime = 2000;

    $("form").submit(function () {
        switch(this.id) {
            case "login-form":
                var $lg_username=$('#login_username').val();
                var $lg_password=$('#login_password').val();
                if ($lg_username == "ERROR") {
                msgChange($('#div-login-msg'), $('#icon-login-msg'), $('#text-login-msg'), "error", "glyphicon-remove", "Login error");
                } else {
                msgChange($('#div-login-msg'), $('#icon-login-msg'), $('#text-login-msg'), "success", "glyphicon-ok", "Login OK");
                }
                return false;
                break;
            case "register-form":
                var $rg_username=$('#register_username').val();
                var $rg_email=$('#register_email').val();
                var $rg_password=$('#register_password').val();
                if ($rg_username == "ERROR") {
                msgChange($('#div-register-msg'), $('#icon-register-msg'), $('#text-register-msg'), "error", "glyphicon-remove", "Register error");
                } else {
                msgChange($('#div-register-msg'), $('#icon-register-msg'), $('#text-register-msg'), "success", "glyphicon-ok", "Register OK");
                }
                return false;
                break;
            default:
                return false;
        }
        return false;
    });

    $('#login_register_btn').click( function () { modalAnimate($formLogin, $formRegister) });
    $('#register_login_btn').click( function () { modalAnimate($formRegister, $formLogin); });

    function modalAnimate ($oldForm, $newForm) {
        var $oldH = $oldForm.height();
        var $newH = $newForm.height();
        $divForms.css("height",$oldH);
        $oldForm.fadeToggle($modalAnimateTime, function(){
            $divForms.animate({height: $newH}, $modalAnimateTime, function(){
                $newForm.fadeToggle($modalAnimateTime);
            });
        });
    }

    function msgFade ($msgId, $msgText) {
        $msgId.fadeOut($msgAnimateTime, function() {
           $(this).text($msgText).fadeIn($msgAnimateTime);
        });
    }
})(jQuery); // End of use strict