Paul,
You mentioned that you're working with ArcGIS Server 10.1, but you've also indicated this is a hosted feature service, can you verify whether this service was published to your own on-premise ArcGIS Server or if it's hosted in the cloud? Registering a local service as an item in your content doesn't necessarily mean it's a hosted service, it just points to the service URL from your on-premise ArcGIS Server.
Would you be wiling to share the service URL or web map ID so that I can take a look?