I can't try the service (I'm on holidays 🙂 ), but as I can see: - There is not a capabilities.xml in the root of the WMS server. Without this file you need the skipgetcapabilities="true" and you can't change the sublayers visibility in TOC. - this WMS service only supports epsg:4269. Is this your spatial reference? As I know, you can't do project on the fly with a WMS service using Flex viewer 😞