Styling a TreeView in Silverlight 3 and Blend 3
Due to a bug in Silverlight, Expression Blend will show an error when using nested Hierarchical Data Templates. There seems to be a problem in the parser, which says the xaml is invalid. But it isn't and the application will run ......
Original post: Styling a TreeView in Silverlight 3 and Blend 3 by at xaml templates - Google Blog Search