Menu hover function repeats

Menu hover function repeats

As you can see in the link provided. When the menu is hovered over a few times. I get this wavy action. Can it be fixed?

http://www.kill-on-sight.com/413/index.html

  1. <script type="text/javascript" src="http://code.jquery.com/jquery-latest.js"></script> <!-- Call latest jquery plugin -->
    <script type="text/javascript"> 
    $(document).ready(function(){
     $('.subnav').width($('.subnav').width()-2);
     $('ul.topnav li').hover(
     function () {
     $('.menu-first', this).addClass('slide-down');
     $('.subnav', this).slideDown(300);
     },
     function () {
     obj = this;
     $('.subnav', this).slideUp(300, function(){ $('.menu-first', obj).removeClass('slide-down'); });
     }
     );
    });
    </script>