com.sun.istack.SAXException2 : Instance ... is substituting "java.lang.Object", but ... is bound to an anonymous type

The problem turned out to be the elaborate nesting of anonymous complex types.

By separating them out as below, the problem went away. And as an added bonus, I got more re-usable code.

    <xs:complexType name="balanceImpactRate">
    <xs:sequence>
        <xs:element name="rate" type="xs:double" />
    </xs:sequence>
    <xs:attribute name="charging-resource-code" type="xs:string"
    use="required" />

</xs:complexType>


<xs:complexType name="balanceImpactRates" >
    <xs:sequence>
        <xs:element name="balance-impact-rate" type="balanceImpactRate"   minOccurs="0"
            maxOccurs="unbounded">
        </xs:element>
    </xs:sequence>
</xs:complexType>