In ubuntu 10.04 when processing a docbook XML file to html, xsltproc fails on a ulink tag. This same file was processed successfully on 8.04 with no error. Any hints?

See the command and output below:

/usr/bin/xsltproc --xinclude --stringparam base.dir chunked/ chunked.xsl book.xml
chprep.xml:161: parser error : EntityRef: expecting ';'
<ulink url='http://ubuntuforums.org/showpost.php?p=4790346&postcount=1'>
^

Note that the caret ('^') points to where xsltproc had trouble. The caret points to the '=' following 'postcount'.

Any clues?