Properties MBean attribues don't update properly

I have this in my jboss-service.xml for a custom MBean that has a Properties attribute:

<attribute name="ConfigurationOverrides" serialDataType="jbxb">
<java:properties xmlns:java="urn:jboss:java-properties"
xmlns:xs="http://www.w3.org/2001/XMLSchema-instance"
xs:schemaLocation="urn:jboss:java-properties resource:java-properties_1_0.xsd">

<java:property>
<java:key>my-data-directory</java:key>
<java:value>${jboss.server.data.dir}/subdir</java:value>
</java:property>

... and more java:property definitions ...

I have other non-Properties attributes in my MBean as well.

This works fine when starting up. My MBean's setConfigurationOverrides(Properties p) method is called with proper values and everything works.

However, if I go to the JMX console, and edit one of my other attributes (simple String attribute), it seems my Properties attribute gets hosed - its values are all screwed up.