Add a Layer from an ArcGIS Online Feature Server that is Shared with the Organisation only. Instantiate the ArcGIS Viewer for Flex 3.0 beta. The Viewer challanges for credentials. On supply of valid Credentials for the Organisation the Viewer responds with "Invalid username/password. Please try again". However if you Log on to the Organisation on ArcGIS Online with the same credentials and then instantiate the ArcGIS Viewer for Flex. The viewer spins up fine.
