XML Schema Validation Errors

Hi

Can some one help me out to find some information about possible errors and
their cause/fix for the XML schema validation by the Xerces parser.

I'm specifically looking for the error
"org.xml.sax.SAXParseException: sch-props-correct.2: a schema cannot contain
two global components with the same name; this one contains two occurrences
of 'http://schemas.myschemas.com/schemadef1,element1'."
The "element1" referred here is a 'ref' in my main xsd.

Thanks

SAM