Today I downloaded WatiN (Web application test in .Net) tools and wanted to run the web test using Visual Studio .Net 2008. I got the following error:
Could not load file or assembly 'Interop.SHDocVw, Version=18.104.22.168, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
If you see this in the future, it is easy to fix it. You can just go to C:\Windows\System32 and copy shdocvw.dll to the bin directory of your current project.
Open your Visual Studio project, add shdocvw.dll in your references and run the test again. The problem will be disappeared.