I had to change in the attr function to check for elem.filter before replacing it :

if (name == "opacity" &&

jQuery.browser.msie && value != undefined ) {

IE has trouble with opacity if it does not have layout

Force it by setting the zoom level

elem.zoom = 1;

// Set the alpha filter to set the opacity

return elem.filter =

(elem.filter ? elem.filter.replace(/alpha\\([^\\)]*\\)/gi,"") : "") +

(value == 1 ? "" : "alpha(opacity=" + value * 100 + ")" );

}