             {
                 systemManager.getSandboxRoot().addEventListener(MouseEvent.MOUSE_MOVE, systemManager_mouseMoveHandler);
                 systemManager.getSandboxRoot().addEventListener(SandboxMouseEvent.MOUSE_MOVE_SOMEWHERE, systemManager_mouseMoveHandler);
+                // MOUSEUP triggers may be added in systemManager_mouseMoveHandler
                 systemManager.getSandboxRoot().addEventListener(Event.RESIZE, systemManager_resizeHandler, false, 0, true);
             }
             

            {
                systemManager.getSandboxRoot().removeEventListener(MouseEvent.MOUSE_MOVE, systemManager_mouseMoveHandler);
                systemManager.getSandboxRoot().removeEventListener(SandboxMouseEvent.MOUSE_MOVE_SOMEWHERE, systemManager_mouseMoveHandler);
                systemManager.getSandboxRoot().removeEventListener(Event.RESIZE, systemManager_resizeHandler);
            }
            
            openButton.systemManager.getSandboxRoot().removeEventListener(MouseEvent.MOUSE_WHEEL, systemManager_mouseWheelHandler);
        }
    } 

    /**
     *  Open the drop down and dispatch a <code>DropdownEvent.OPEN</code> event. 

    protected function systemManager_mouseMoveHandler(event:Event):void
    {
        var target:DisplayObject = event.target as DisplayObject;
        var containedTarget:Boolean = isTargetOverDropDownOrOpenButton(target);
        
        if (containedTarget)
            return;
        
        // if the mouse is down, wait until it's released to close the drop down
        if ((event is MouseEvent && MouseEvent(event).buttonDown) ||
            (event is SandboxMouseEvent && SandboxMouseEvent(event).buttonDown))
        {
            systemManager.getSandboxRoot().addEventListener(MouseEvent.MOUSE_UP, systemManager_mouseUpHandler);
            systemManager.getSandboxRoot().addEventListener(SandboxMouseEvent.MOUSE_UP_SOMEWHERE, systemManager_mouseUpHandler);
            return;
        }
        
        closeDropDown(true);
    }
    
    /**
     *  @private
     *  Called when the dropdown is popped up from a rollover and the mouse is released 
     *  anywhere on the screen.  This will close the popup.
     *  
     *  @langversion 3.0
     *  @playerversion Flash 10
     *  @playerversion AIR 1.5
     *  @productversion Flex 4
     */ 
    protected function systemManager_mouseUpHandler(event:Event):void
    {
        var target:DisplayObject = event.target as DisplayObject;
        var containedTarget:Boolean = isTargetOverDropDownOrOpenButton(target);

        // if we're back over the target area, remove this event listener
        // and do nothing.  we handle this in mouseMoveHandler()
        if (containedTarget)
        {
            systemManager.getSandboxRoot().removeEventListener(MouseEvent.MOUSE_UP, systemManager_mouseUpHandler);
            systemManager.getSandboxRoot().removeEventListener(SandboxMouseEvent.MOUSE_UP_SOMEWHERE, systemManager_mouseUpHandler);
            return;
        }
        
        closeDropDown(true);
