ActionScript :: Flex - RemoteObject Response Headers?

I am in the process of writing an application in Flex 3.3, using the Cairngorm framework, for deployment as an AIR application. The application heavily utilizes RemoteObject services to get data from a web server.Each of my service delegates extends a common class which provides a method for calling service methods on the RemoteObject.So, where I previously usedServiceLocator.getInstance().getRemoteObject('myService').myOperation.send();I instead usethis.send('myOperation', 'myService');I use this method instead of calling the RemoteObject operations directly because this method adds another, global, responder to the operation call. This extra responder analyses data in the headers of reponse from the server.

Or at least it should -- this is where the problem is. In the result data (event as mx.rpc.events.ResultEvent) the headers property is always null despite the headers definitely being sent from the server.