The 9.3 Final release version of the mobile application (PPC version) does not work with mobile service that is secured by token-based security.
The application returns a message saying "Error opening mobile service". For testing purpose, download and open the mobile project named "RedlandsHydroSecured" from mobilebeta.esri.com/arcgis, which encapsulates a token-secured mobile service with the following URL: http://mobilebeta.esri.com/ArcGIS/services/Secured/RedlandsHydroSecured/MapServer/MobileServer.