Guidance Automation Extensions: Error 1001

If you get an InvalidOperationException saying that "Operation is not valid due to the current state of the object" when installing the Guidance Automation Toolkit (or any other guidance package, like the Smart Client Software Factory, for example), check whether your cmd.exe has been configured to automatically set Visual Studio environment variables. Look if the registry key "HKLM\Software\Microsoft\Command Processor\AutoRun" is set to something like "%VS90COMNTOOLS%vsvars32.bat" and remove it for a while (while you install the guidance packages).

Don’t ask why. Just try, it works. It saved me from reinstalling Visual Studio and all the other stuff.