I would probably write to them and clarify the situation with them just to make sure If you can explain the situation they shouldn't ban you... and even then, knowing is probably better than sitting around not knowing if the account is going to be banned.

Having been a moderator on other sites it is actually pretty common for people with the same IP to log on, especially on the bigger and more popular forums. As long as they can explain that and don't show any suspicious activity it is usually left alone. Often it just takes one or two PMs to explain the situation.