If the QueueBot stops responding after a chat, it my be due to the logging. If you have logging to a Notes database setup, check your debug log for the QueueBot. If the last line is:
cWriteToNotes.InitNotesSession() has started
then you have run into this issue. Be sure to give the QueueBot at least one minute to log to the Notes database. If after sufficient time, nothing has happened, then you must restart the machine the QueueBots are running on. This issue will not reappear sproadically. It only sometimes occurs when you have recently upgrading IAF QueueManager, or if a Notes client has behaved unexpectdaly on your machine. This issue is related to Notes. Another symptom of this is that you can not start the Notes client at this point until you restart.