Ola Karlsson had to debug some performance issues in an existing Silverlight app and he decided to share with you this problem and its solution which is quite tricky.
On start, the app would do a number of calls to different methods on a WCF service, this to populate the UI with the necessary data. Recently one of those services had been changed and was now taking quite a bit longer than it used to. This was resulting in quite a long loading time for the whole UI, which was set up so it wouldn’t let the user interact with anything, until all the service calls had finished.