On querying a point or polygon feature in an ArcGIS server 9.3.1 application developped using Silverlight 4, the application either hangs or takes abnormally long time to respond. However, when the query is off, the features appear immediately and behaves normal. The same is not the case when we run the application in Silverlight 3, it runs smooth and the response to query is fast. What could be the reason?