Adam, have you solved this problem? I can't give you a solution but can provide more information.
Evidently there's a ManagedBean set up for each "managed object" in Catalina (e.g. Valves, Realms, etc.). See
http://jakarta.apache.org/tomcat/tomcat-4.1-doc/catalina/funcspecs/mbean-names.html. I ran into this issue when setting up a new Realm. Evidently all the information listed on the page referenced above comes from an xml file located at org\apache\catalina\mbeans\mbeans-descriptors.xml. (I found it by following that stack trace. It's read by org\apache\catalina\mbeans\MBeanUtils.java, if you have the source.)
What I did was to modify this file, and save it as TOMCAT_HOME\server\classes\org\apache\catalina\mbeans\mbeans-descriptors.xml, so it gets "found" in the classpath before the one in catalina.jar.
I just modeled my entry on a similar class.
My hunch is that this is used to define/pass parameters from server.xml and web.xml. However, there must be a more elegant way to handle this!
It was certainly not an issue in 4.0. :roll: