XWorkConverter uses ObjectFactory.getObjectFactory() when loading default TypeConvertors in its constructor. However, currently in struts-default.xml, the ObjectFactory has its static injections after the XWorkConverter does, so when the XWorkConverter is constructed, it ends up using the default ObjectFactory (as set in DefaultConfiguration.reload()).
The fix is easy, just move:
<bean class="com.opensymphony.xwork2.ObjectFactory" static="true" />
to be the first static injection.
Also, while you are there,
<bean class="com.opensymphony.xwork2.util.XWorkConverter" static="true" />
should also be moved to be before
<bean class="com.opensymphony.xwork2.util.OgnlValueStack" static="true" />
This is because XWorkMapPropertyAccessor staticly creates an instance of XWorkMapPropertyAccessor which in turn staticlly gets an instance of the XWorkConverter. (Necessary until the XWork 2 issue is resolved: http://jira.opensymphony.com/browse/XW-492)