                 
         private function hidePopUp() : void {
             if (isDropDownOpen) {
-                popUp.popUp.removeEventListener(FlexMouseEvent.MOUSE_DOWN_OUTSIDE, onMouseDownOutside);
+                popUp.popUp.removeEventListener(FlexMouseEvent.MOUSE_DOWN_OUTSIDE, onMouseDownOutside);                
+                systemManager.removeEventListener(MouseEvent.MOUSE_WHEEL, onMouseWheel);
                 popUp.displayPopUp = false;
             }
         }

                    list.selectedIndex = -1;
                }
                                        
                popUp.popUp.addEventListener(FlexMouseEvent.MOUSE_DOWN_OUTSIDE, onMouseDownOutside);
            }
        }
        

            popUp.updatePopUpTransform();            
        }
        
        private function onMouseWheel(event : MouseEvent) : void {
            
            trace ("event.target=", event.target);
            if (!(DisplayObjectContainer(list).contains(DisplayObject(event.target)) && event.isDefaultPrevented())) {
                hidePopUp();
            }
        } 
            
        private function onMouseDownOutside(event:FlexMouseEvent) : void {            
            var mouseDownInsideComponent : Boolean = false;            
            var clickedObject : DisplayObjectContainer = event.relatedObject as DisplayObjectContainer;
