Medieval 2: Total War Message Board  

I had the same problem and if you have FOW turned on (so the map only shows what you've actually discovered) - then when you sail a fleet of caracks over (and it has to be carracks) - then it will give you 2 different messages - one that you've discovered the new world - and then when you come close enough to an Aztec settlement it will tell you that hte new world is inhabited. That should be all you need.

YOU CAN'T GET THERE BUT IF YOU GET YOU WIL NOT SURVIVE

That doesnt work.