Firstly, look into using acceptConfirmationForObject in place of the confirmation checker.
Secondly, you have a potential bug in using the disconnected event to log into a new account. The disconnected event can also be emitted if the connection to Steam drops temporarily but will be automatically re-established. You should probably set a flag when you call logOff() so you know if the disconnected event was in response to that.
Finally, to your main question, you should call manager.shutdown() when you log out of an account before logging into a new one. That should solve your problems.
Derp. reacted to Dr. McKay in Switching Users?