Sometimes when Mingle does not shutdown cleanly, upon starting up again you will encounter a BadMagicException and it will not be able to bring the instance up.
If the happens, you can delete the message queue data folder to enable successful startup.
In your mingle.dataDir folder, find the folder called activemq-data
Delete this folder entirely. Mingle will have to be down for this to work.
Now try to start it up and it should come up fine. If you still encounter a problem, contact the support team.