All of a sudden I'm getting Error 2 on the code-signing step in SetupBuilder 10.

I renewed the code-signing certificate some months ago, and it has been working fine since then, but now, suddenly, it doesn't. I have the path to signtool.exe set, and for the time stamp I'm using

http://timestamp.comodoca.com/authenticode

What does 'Error 2' mean?

David Webber