http://www18.imperiaonline.org/imperia/game_v5/game/help/?page=glossary&term=387#term-387So if you change the password of one of your accounts, part of your global account, the password becomes valid for all global account accounts.
The weird thing here is that with a different username in realm 82, so consequently not part of the global account, you still see login option 82 when you intend to enter the realm 30 account. Thus, I will need usernames so I could check.