Flex Builder 2: trouble with httpservice after adding ViewStack

all I did was add a login screen to the dashboard sample and the requisite VBOXing and  viewstack and all of a sudden the HTTPservice can't get thru to the results.xml
I am an old VB type trying to dust off my OOP skills (yeah, not that VB is true OOP.  wah-wah) and I'm thinking that with adding the VBox and ViewStack to manage display of the screens that now the HTTPservice resulthandler has lost contact with the embedded mxml scripts which actually pass the data to the graph controls.

I get this error at runtime...

TypeError: Error #1009: Cannot access a property or method of a null object reference.
      at dashboard/::resultHandler()
      at dashboard/__srv_result()
      at flash.events::EventDispatcher/flash.events:EventDispatcher::dispatchEventFunction()
      at flash.events::EventDispatcher/dispatchEvent()
      at mx.rpc.http.mxml::HTTPService/http://www.adobe.com/2006/flex/mx/internal::dispatchRpcEvent()
      at mx.rpc::AbstractInvoker/http://www.adobe.com/2006/flex/mx/internal::resultHandler()
      at mx.rpc::Responder/result()
      at mx.rpc::AsyncRequest/acknowledge()
      at ::DirectHTTPMessageResponder/completeHandler()
      at flash.events::EventDispatcher/flash.events:EventDispatcher::dispatchEventFunction()
      at flash.events::EventDispatcher/dispatchEvent()
      at flash.net::URLLoader/flash.net:URLLoader::onComplete()