Java Client APIs to get hierarchy of children and subchildren?

I am trying to basically build a recursive gathering of Child work items ...so I start with one and want to build up (basically) an ArrayList of that work item, it's children, the children of those children, the children of those children, etc.

I am hitting odd Assertion errors trying to recurse using WorkItemCopyManager to get a WorkingCopy of my IWorkItem (child) so that I can then getReferences() since it seems references are not on the IWorkItem but only in the WorkingCopy?

Susan