DOCBOOK-APPS: Docbook XML 4.1.2 parse problem

Hi,
I am trying out Norman Walsh's XSL style sheets for docbook but am
having some problems with Xalan 1.2. I'm not sure which Xerces comes
with xalan 1.2.

xslt.sh tbook.xml mystyle.xsl
========= Parsing file:/home/maxwell/book/mystyle.xsl ==========
Parse of file:/home/maxwell/book/mystyle.xsl took 62148 milliseconds
========= Parsing file:/home/maxwell/book/tbook.xml ==========
http://www.oasis-open.org/docbook/xml/4.0/docbookx.dtd; Line 66; Column
9
XSL Error: Could not parse file:/home/maxwell/book/tbook.xml document!
XSLT: Recursive reference "%dbnotn;". (Reference path:
(top-level)-%dbhier;-%dbnotn;-%dbnotn;)
Xalan: was not successful.
XSLProcessor: done

xslt.sh is just a simple script to call the xalan processor. tbook.xml
is a very simple file which validates with nsgmls and uses the 4.1.2
version of docbook. The mystyle.xsl is the wrapper that calls the
docbook/xhtml/docbook.xsl style sheet.

Does this look familiar to anyone?

Thanks for any help,

Eric
MilagroSoft Inc.