在外框上时，Firefox Mac上的Flash Player无法提供正确的鼠标位置

package
{    
    import flash.display.Sprite;
    import flash.events.Event;

    [SWF(width=\"750\", height=\"520\", frameRate=\"40\", backgroundColor=\"#000000\")]

    public class HelloWorld extends Sprite
    {
        private var _mouseX:Number;
        private var _mouseY:Number;

        public function HelloWorld()
        {
            addEventListener(Event.ENTER_FRAME, onEnterFrame);
        }

        public function onEnterFrame(event:Event):void
        {
            if ((mouseX != _mouseX) || (mouseY != _mouseY))
            {
                _mouseX = mouseX;
                _mouseY = mouseY;
                trace(_mouseX, _mouseY);
            }
        }
    }
}