Jabber user remains logged in

10.6 Server: iChat Service running.

User logged in once from their MBP (10.6) successfully, but no matter whether they actively log out from iChat, or just close the lid and take it with them, they remain logged into the server and appear as present to the other users, which causes some issues since they're not really. On a service start/stop they disappear, but immediately come back online, even though they are not.

When they do show back up and log in, they do so successfully, but they do not receive the messages sent in their absence.

How can I manually disconnect that user from the server and restore them to working order so they come and go as the other users do?