Why do I get “An error occurred while validating. HRESULT = '80004005'” when building a setup project?

Question

Why do I get the following error when building a setup project?

An error occurred while validating. HRESULT = \'80004005\'

Answer 1

While simply removing and re-adding the project dependencies will work in many cases, it is important to note that:

The error message "An error occurred while validating. HRESULT=80004005." usually happens when project is referenced to the other project which is not added into the currect [sic] solution. Setup project only supports dependency projects within same solution.1