I believe you are referring to the following issue:
This has been investigated and resolved in the current releases:
v220.127.116.11 for VS 2010 and v18.104.22.168 for VS 2012
I have also conducted regression testing to verify that the Message Bus is functioning properly.
Note that while the bus will not create memory leaks if you don't call UnRegister, it is good practice to unregister subscribers so they do not continue to receive messages..