All Javascript on site performs horribly Slow in Firefox 4 when transparent PNG’s are present on the page

ETA UPDATE: I’ve found that if I remove all the transparent .png files from my site, there are about 5, it runs fine. THAT is odd. And up-votes would be very helpful, I tested it on a few more computers, and 4/15 have this issue. Thanks! Any ideas?

Runs fine on PC Firefox and all other browsers, but on 4/15 computers in Mac Firefox, the Javascript is just terribly slow, specifically the menubar. I tested them both outside the site and they worked fine. This has been an ongoing problem for quite some time, no idea how to solve it. Updated, problem goes away if I remove transparent PNG’s from the site, like the banner in the top left.

My site: http://thenozzle.net/

All of the javascript is a bit slower then in other browsers, the two largest ones are menubar and video player. I can’t ignore it at this point.

I’m wondering if it’s something wordpress is adding, because the js works fine elsewhere.

Any ideas?

ETA: Here’s my JS file:

http://thenozzle.net/wp-content/themes/twentyten/scripts.js

ETA: Here’s my menubar code

$(function() {
    $('#sdt_menu > li').bind('mouseenter',function(){
        var $elem = $(this);
        $elem.find('img')
             .stop(true)
             .animate({
                'width':'170px',
                'height':'170px',
                'left':'0px'
             },400,'easeOutBack')
             .andSelf()
             .find('.sdt_wrap')
             .stop(true)
             .animate({'top':'140px'},500,'easeOutBack')
             .andSelf()
             .find('.sdt_active')
             .stop(true)
             .animate({'height':'170px'},300,function(){
            var $sub_menu = $elem.find('.sdt_box');
            if($sub_menu.length){
                var left = '170px';
                if($elem.parent().children().length == $elem.index()+1)
                    left = '-170px';
                $sub_menu.show().animate({'left':left},200);
            }
        });
    }).bind('mouseleave',function(){
        var $elem = $(this);
        var $sub_menu = $elem.find('.sdt_box');
        if($sub_menu.length)
            $sub_menu.hide().css('left','0px');

        $elem.find('.sdt_active')
             .stop(true)
             .animate({'height':'0px'},300)
             .andSelf().find('img')
             .stop(true)
             .animate({
                'width':'0px',
                'height':'0px',
                'left':'85px'},400)
             .andSelf()
             .find('.sdt_wrap')
             .stop(true)
             .animate({'top':'25px'},500);
    });
});