Make sure it's your settler - I tried to play a game on the Earth map as America, and Monty invaded with a stack of two Jaguars on a city that was defended by a warrior (I had a axeman going to the city, but it would take too long), so I WB'd in a axeman, but unfortunatly, it belonged to Hatty. I had to delete it, but the damage was done - she had contact with both me and Monty. I had to abandon the game because I was no longer isolated.