用jquery.easing.1.3后原下拉菜单无效？如何解决？

$(document).ready(function(){
        $('#slider1').bxSlider({
            pager: true,
            pagerSelector: '#my-pager',
            controls: false
        });
    // dropdown menus
$('.menu ul li').hover(
    function () {
        //show its submenu
        $('ul', this).slideDown(300);
    }, 
    function () {
        //hide its submenu
        $('ul', this).slideUp(300);         
    }
);
    });