[Angrist]

I like to see it as they do in the X-Men cartoon, a few episodes with Bishop I think he's called. He travels back in time to change something, comes back to the future and stuff is changed. But he's the only one who notices it... for the rest of the people it's just what they've grown up with. The present doesn't suddenly change when you go back.
And I like the idea of BttF2, where a second timeline is created.

But yeah, this is exactly what you have with every time travelling story. It makes no sense. Paradoxen within paradoxen.