This is another way where the map editor crashes. It happens every time I select a player to move their start location when I have set the number of players to a number lower than that. EXAMPLE: I set the number of players to 3 and then go brush->player->player 4.
I just thought it would be helpful to let you know; I know the problem can be avoided, but some people might not know why it's crashing and so maybe there could be a little pop-up that says you cannot do that.