1) Install Silverlight 2.0
2) Make sure you have done all entries required for Silverlight 2.0 in web.config file of that site.(All entries for Ajax)3) Add ScriptManager into web part before render silverlight component
4) Add following additional entry in assemblies section of web.config<add assembly="System.Web.Silverlight, Version=2.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
5)Add System.Web.Silverlight.dll in Global Assembly Cache.This dll is available in following path C:\Program Files\Microsoft SDKs\Silverlight\v2.0\Libraries\Server
