Are those built-in queues (like the JMS flow queues) or are there unexpected consumers on your own queues? If you ever have a problem like this with ESB, there's no need to uninstall -- just deleting everything in the data/ directory gives you a clean environment to start with.
Just two additional questions -- do you have other developers working with the same SAs and is multicast enabled on your embedded ActiveMQ instance (it is by default, unless you have disabled it)?
I have been trying to reproduce the error you talked about but always I get the expected consumer number.
Could give us more details about the implementation? How are you creating the consumers and queues?