Started with a default Prism Shell project using http://blogs.msdn.com/b/dphill/archive/2009/05/29/prism-quick-start-kit.aspx and all was working as expected. I began making changes and modifications and now the application is started twice, however the protected override DependencyObject CreateShell() method in the Bootstrapper is only called once. The constructor(s) in the ShellView are being called twice. Once for the default constructor and once for a constructor taking an instance of the ShellViewModel. I can't seem to locate the cause for this....however my guess is that resolution will be trivial. Hopefully someone can help...