When I installed Visual Studio 2008 with pre-existing Silverlight plugin, I suddenly could no longer create new Silverlight project from within Visual Studio.
This was the error message that I got Could not load type ‘Microsoft.VisualStudio.Web.Silverlight.IVSilverlightService’ from assembly…
Doing some research led me to BradleyB’s Weblog. Following the steps from his blog post seems to solve the above error message. However, I then got a new error message “Object reference not set to an instance of an object.”
Doing a devenv /resetskippkgs on the command prompt helped me fix the second error message.