"The 1th supplied input is not a schema document: its type is N=" from SchemaUtils.loadSchemaTypes

I am getting the following error when trying to parse a schema using  SchemaUtils.loadSchemaTypes.

15:25:44,644 ERROR [SoapUI] An error occurred [Thread qtp1092591822-28: The 1th supplied input is not a schema document: its type is N=], see error log for details
15:25:44,651 ERROR [SoapUI] An error occurred [com.eviware.soapui.impl.wsdl.support.xsd.SchemaException], see error log for details
org.apache.xmlbeans.XmlException: Thread qtp1092591822-28: The 1th supplied input is not a schema document: its type is N=
at org.apache.xmlbeans.impl.schema.SchemaTypeSystemCompiler.compile(SchemaTypeSystemCompiler.java:211)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.apache.xmlbeans.XmlBeans.compileXmlBeans(XmlBeans.java:667)
at org.apache.xmlbeans.XmlBeans.compileXsd(XmlBeans.java:553)
at com.eviware.soapui.impl.wsdl.support.xsd.SchemaUtils.buildSchemaTypes(SchemaUtils.java:287)

I have trapped the exception in Eclipse and the problem seems to be caused by the default schemas added by the loadSchemaTypes. My schema (which is 0 in the array provided to org.apache.xmlbeans.impl.schema.SchemaTypeSystemCompiler.compile and of type schmaDocumentImpl) is followed by 10 added by SoapUI of type XmlAnyTypeImpl. It complains about the first of these which is the following:

<xs:schema targetNamespace="http://www.w3.org/2004/08/xop/include" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:tns="http://www.w3.org/2004/08/xop/include">
<xs:element name="Include" type="tns:Include"/>
<xs:complexType name="Include">
<xs:sequence>
<xs:any namespace="##other" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="href" type="xs:anyURI" use="required"/>
<xs:anyAttribute namespace="##other"/>
</xs:complexType>
</xs:schema>

I could not find anything on this online so suspect the issue is mine......but it's not clear to me what I'm doing wrong. Any insights appreciated.