Re: The black belt Issue (thoughts)
With the other two posters - I think it's a miss-applied phrase that only makes any sense in context.
While it's not one of my favourites (in fact, it's up there with it takes x years to master y) I've always understood it to mean that it takes you until your black belt to realise just how little you actually know. A bit like completing any course in absolutely anything, you need a certain level of competence before you can tell how woefully inadequate you truly are.
Peter, not warped, just slightly bent (guilty of taken long long time to get the black belt, ok perhaps too long, but I blame the parents)