"Resolved bugs: Large requests by tasks are failing. If a task creates a Web request with greater than 2048 characters in the URI, the task will use POST (instead of GET) to submit the request."
I have a client who is working with the Silverlight API 2.2 and ArcGIS Server 10 SP2. They are running into an problem wherein their application seems to be making GET HTTP requests to ArcGIS Server that exceed the maximum URI length of 2048 characters. When this happens this leads to errors in the application, and then the map vanishes from the viewer menu.