After installing Silverlight 3 Beta 1 I got the following error when compiling a Silverlight Project which has a WCF Service reference:

Unable to find DynamicTypeService

I remembered I had a similar problem back with a Beta version of Silverlight 2.
The blog of Tim Anderson helped me out twice.

The following steps did the trick:

  1. Remove this file:
    \Program Files\Microsoft Visual Studio 9.0\Common7\IDE\Microsoft.VisualStudio.ServicesProxy.dll
  2. Uninstall Silverlight 3 Beta / SDK
  3. Reinstall Silveright 3 Beta