It was to do with applying a particular aspect of the theory to a particular problem. I guess the lesson is the old one that theories can't always be usefully applied to every problem in practice, even when the theories are perfectly true. "There is no difference between theory and practice - in theory."
I'm sorry, I (mysteriously) can't disclose specifics. Actually, I think it would be of interest to vanishingly few people, and as I explained it, even the remaining ones would quietly slip away.
