If a conversation times out, and the other party sends
a message, pebrot will create a new tab for it, instead
of re-using the old tab.
This was added on 2007-01-04 and released as part of Pebrot 0.8.9.
However, if the person's position changes in the user list, Pebrot gives
a "Message was not received" error and one has to close the chat window
and reopen it. At least I think this is the cause.