Cannot save or export XML data??
 

When I tried to export a range to XML in excel 2003, it pops out an
error message:
Cannot save or export XML data. The XML maps in this workbook are not
exportable.

I tried to verify the schema, it turns out:
xxx_Map is not exportable because it contains the following:
.. List of lists
.. A mapped element's relationship with other elements cannot be
preserved

The schema also contains elements which have not been mapped into the
spreadsheet...

What could be the solution?