This problem occurs during a roundtrip operation where a new SDO Type is created, then an instance DO is created from that type. That instance DO is then serialized to an XML document. Then, using XMLHelper.load(String), the document is loaded into an XMLDocument object. When that object is inspected, the rootElement member is not set properly, implying there is either something wrong with the serialization of the DO or the deseriazliation of the xml document.
Investigation is underway.