<serverItem url="http://myservice/arcgis/rest/services" matchAll="false" username="Myuser" password="Mypass" tokenUrl="http://myservice/arcgis/tokens" timeout="30" />
I'm having a similar issue. I have configured the silverlight proxy page (for 3.3) per ESRI's instructions and confirmed with the ping url, but when adding a layer with the "use proxy" checked I get an "Unable to connect to https:// .... " error. I can connect via browser to the secured map services with the username/password, and can connect and login with secured services in the Silverlight Viewer authoring tool, but cannot get the proxy page working.
Can an ESRi staff member address these questions?
Thanks,
Paul