That's interesting. Technically speaking they should kill just because your IP logs on, since IPs can cover pretty big areas. Then even if they are locked on your comp. IP they still shouldn't ban every account, unless you've done something really terrible.
A singular IP points to a single computer within a timespan. While that IP may belong to someone fifty miles away tomorrow, if he logs into the accounts within a few minutes or hours from each other, the odds are highly in favor of it being the same person.