DOCBOOK: Spanish Text

I just recieved a Docbook XML document in Spanish.  I'm trying to 
transform the document to HTML with SAXON, as I do with the English 
documents, but it has trouble with the extended ascii characters as follows:

<.xml c:/docbook/docbook-xsl/html/mdp.xsl > getstarted-howto.html
Error at byte 248 of 
file:/C:/cygwin/home/Administrator/mapserver_docs/getstarted-howto_es.xml:
  Error reported by XML parser: bad continuation of multi-byte UTF-8 
sequence (code: 0x74)
Transformation failed: Run-time errors were reported


I know that I could have the author replace all the offending characters 
with entity references (&aacute;), but I don't want to do this unless 
it's necessary.  Is there any alternative?

Thanks,
Jamie Smedsmo