TFS Error: MSB4018 The “BuildShadowTask” task failed unexpectedly

There seams to be a problem in MSBuild when you add an “Accessor” as part of a Unit Test project. C:Program FilesMSBuildMicrosoftVisualStudiov9.0TeamTestMicrosoft.TeamTest.targets(14,5): error MSB4018: The “BuildShadowTask” task failed unexpectedly. System.IO.FileLoadException: API restriction: The assembly ‘file:///C:WINDOWSMicrosoft.NETFrameworkv2.0.50727System.Web.dll’ has already loaded from a different location. It cannot be loaded from a new location within the same appdomain. at […]