Jquery.css performing unwanted flickering effect on IE and Webkit (Chrome, Safari) but Firefox is ok
===

I have the following code:

    $(document).ready(function(){
       $(window).scroll(function(){    
          Topo =  $(window).scrollTop();
          function ScrollObjsASodaAnimate(){
             ObjScrollASoda.css({
                 'marginTop' : (Topo - 800)+'px'
             });
          }
       });
    });

The website is this one : http://wearesoda.com/wearesoda/#a_soda

In the blue section, there is a blue can that will "scroll" with the page making a parallax-like effect. Here is the problem, as I'm just setting the css while the user scrolls the page, only in Chrome (and other webkit browsers) it happens the can to show a flickering effect (unwanted). And I noticed it doesn't happend in Firefox.
Does anyone knows how to avoid this "flickering" effect ??

Here is a video explaining better what's happening : 
http://www.youtube.com/watch?v=SqDmOx6XY-M

(Sorry for my english)