Somtimes,following code dosen't work in IE7:

	fix: function(event) {
		// Fix target property, if necessary
		if ( !event.target && event.srcElement )
			event.target = event.srcElement;

		// Calculate pageX/Y if missing and clientX/Y available
		if ( event.pageX == undefined && event.clientX != undefined ) {
			var e = document.documentElement, b = document.body;
			event.pageX = event.clientX + (e.scrollLeft || b.scrollLeft);
			event.pageY = event.clientY + (e.scrollTop || b.scrollTop);
		}

"b" is null on page initialization time(though document.body is not null),so expression:

(e.scrollLeft || b.scrollLeft) dosen't evaluate and throws "Object required" exception in "b.scrollLeft",because "e.scrollLeft" is "0" in that time.

This bug is repeatable,if reload the same page several times,it popups sometimes.