Jquery in vB4

[Twilkey]

This code works fine in vB3, but not in 4. I am not sure why, but when I add this code in my headerinclude template and save it the page just loads to an empty page, and it doesnt actually get to saving the changes. I know it is this code, because the template saves fine when I take this out, so I just need to know why this would stop the template from saving.

<script type="text/javascript"> 
$(document).ready(function(){

    $("ul.subnav").parent().append("<span></span>"); //Only shows drop down trigger when js is enabled - Adds empty span tag after ul.subnav
    
    $("ul.topnav li span").click(function() { //When trigger is clicked...
        
        //Following events are applied to the subnav itself (moving subnav up and down)
        $(this).parent().find("ul.subnav").slideDown('fast').show(); //Drop down the subnav on click

        $(this).parent().hover(function() {
        }, function(){    
            $(this).parent().find("ul.subnav").slideUp('slow'); //When the mouse hovers out of the subnav, move it back up
        });

        //Following events are applied to the trigger (Hover events for the trigger)
        }).hover(function() { 
            $(this).addClass("subhover"); //On hover over, add class "subhover"
        }, function(){    //On Hover Out
            $(this).removeClass("subhover"); //On hover out, remove class "subhover"
    });

});
</script>