Exception with same type collections and location= [TESTCASE]

I have attached a testcode which demonstrates the problem. The testcase model
is as follows: A RuleBase has a collection of Rules, and each Rule has a
collection of AllowHosts and DenyHosts (both of type Host).

Castor marshalls the objects correctly but throws a SAXException when parsing
the XML it generated. I think this is due to the fact that both collections are
the same type, if you comment out the DenyHosts field definition then it works.

I have tried to fix this but I'm not very familiar with the Castor code.