A NullPointerException is thrown by InvokerLocator.resolveHost if a null host is passed in. (Line 333 of InvokerLocator.java for the 2.2.2SP4 tag)
This was observed when running JBEAP 4.3 on a laptop that has a VPN client installed. JBoss was configured to bind to all interfaces (-b0.0.0.0) and iIt appears that this configuration results in a null host being passed to resolveHost. resolveHost then does a host.indexOf("0.0.0.0") which throws the NPE.
On the laptop in question, this can be worked around by explicitly binding the the required IP address, rather than binding to all, but the code should handle the case where a null host is passed in more gracefully.