http://developers.de/blogs/damir_dobric/archive/2009/08/06/silverlight3-breaking-change.aspxIf you have developed SIlverlight < 3.0 apps, you might (sometimes) notice that some of them will not work on Silverlight 3.0 One of issues which causes this problem is the fact the Microsoft has decided to remove Silverlight.Dll from Silverlight SDKenCommunityServer 2008 SP1 (Build: 30619.63)