“Unspecified error” in Visual Studio 2008 when trying to view project properties

Question

When I set my active solution from Win32 to x64, I cannot build the project or view the properties.

When I try to build my project, it is skipped.

When I try

Answer 1

The x64 components for Visual Studio 2008 had not been installed on the second computer. Installing those solved the problem.

(There are a lot of unhelpful hits in Google when searching for a solution to this problem. Hopefully this helps someone else in the future.)