Hi Mike,
I can't tell you what is happening, but the fact that the innermost Exception is a SocketException("Connection reset") indicates that the connection was closed at the other end. Do you have a firewall between the client and server? Do you see any indication in server.log that connections were closing on the server?
I don't know what the two versus four connections means. You might pose the question on the JBossMessaging users forum.
-Ron