[flexcoders] popupbutton in viewstack/canvas

[grimmwerks]

Does the popupbutton NOT work within a canvas in a viewstack?
I've gotten this code -- doesn't work in the viewstack but everywhere  
else is fine...:

  <mx:PopUpButton id="popUpButton" horizontalCenter="0" top="200"
                label="Click on me"
                openAlways="true">
            <mx:popUp>
                <mx:TitleWindow id="titleWin"
                        height="200" width="200"
                        showCloseButton="false"
                        verticalScrollPolicy="on"
                        horizontalScrollPolicy="off">

                </mx:TitleWindow>
            </mx:popUp>
        </mx:PopUpButton>