A solution was just converted from VS 2008 to VS 2010. My VS 2010 build is failing with the popular "The type or namespace X could not be found". When I go to the project and go to Add References and add the appropriate project dll, the class name appears in blue text as if .NET found the correct class. However, when I go to the Build menu and select "Build Solution" I get the "namespace not found error" and the class name is no longer blue.

Thanks.