XML_ERROR_INVALID_TOKEN

Hi everyone! i write cause i've a problem parsing a wikipedia xml dump.
XML_Parse returns error and when i use XML_GetErrorCode i get error n°4
which means something like: "XML_ERROR_INVALID_TOKEN not well-formed"

The head of the wikipedia dump begins like: "<mediawiki xmlns="
http://www.mediawiki.org/xml/export-0.3/" xmlns:xsi="
http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="
http://www.mediawiki.org/xml/export-0.3/
http://www.mediawiki.org/xml/export-0.3.xsd" version="0.3" xml:lang="es">
  <siteinfo>
    <sitename>Wikipedia</sitename>"

My question if i've to validate this with and schema (XSd) or if any of you
know how to bypass this error cause it doesnt seem to parse nothing.
THx in Advance!