"One or more errors encountered while loading the designer. The errors are listed below. Some errors can be fixed by rebuilding your project, while others may require code changes. TypeLoad failure. Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information"
Looks familiar? There's a hotfix for that, and you may want to turn off "edit and continue" in VS 2005. Yep. Stable.