I was just thinking about the situation in the Church and I wondered if it might be possible that Paul VI WAS an anti-Pope (I am not a sede). If he was, it invalidated VII and all of the modern errors and while the Popes who followed him could still be valid Popes (even if Paul was an anti-Pope) most of their errors would be due to a mistaken belief that he wasn't - thus feeling that they had to accept VII as valid.
Any thoughts?