Maybe a 'Universe' is the amount of mass it requires to form a Black Hole which cannot be curved back to a white-hole elsewhere in the same universe, and effectively drops through to another 'energy level' or the like? For all we know, there might be countless universes, expanding out in an energy level as they pour through the entry point, cooling off, contracting and falling through to the next 'level' where they do it all over again.
Ok, so that's more powered by imagination than education, but, the real problem with the birth of the Universe is not that no theories make sense, it's that quite a lot of theories do, in theory, but we are never really going to be able to test them, they contain objects too small and too big to conceive in anything other than Model form. As Trashman says, the birth of a Universe is a very 'odd' moment in history, and we may never ever know what actually 'triggered' the change even if we figure out the nature of the expansion.
Edit: Actually, thinking about it, that idea could not possibly work

Cookie for anyone who can guess why
