Any known problems with Chinese JavaHelp?

Hello,

I have a problem with Chinese DocBook (utf-8) and JavaHelp.
What I do is:

$ xsltproc /usr/share/xml/docbook/stylesheet/nwalsh/javahelp/javahelp.xsl \
  debian-jigdo-mini-howto_ch.dbk
$ java -jar $JAVAHELP_HOME/demos/bin/hsviewer.jar -helpset `pwd`/jhelpset.hs

The latter command gives me some error messages:

DocumentParser Error: Expecting an attribute (2)
(multiple times)
Parsing failed for file:/.../jhelptoc.xml
<tocitem target="authorship" text="?&#27690;?&#29242;?&#21811;?"/>
      <tocitem target="acknowledgements" text="&#31073;&#37061;"/>
(and so on)
Exception caught while parsing
file:/.../jhelptoc.xmljava.util.EmptyStackException
Exception in thread "Thread-1" java.lang.NullPointerException
        at
javax.help.MergeHelpUtilities.mergeNodeChildren(MergeHelpUtilities.java:81)
        at
javax.help.plaf.basic.BasicTOCNavigatorUI.loadData(BasicTOCNavigatorUI.java:208)
        at
javax.help.plaf.basic.BasicTOCNavigatorUI.access$000(BasicTOCNavigatorUI.java:65)
        at
javax.help.plaf.basic.BasicTOCNavigatorUI$NavSwingWorker.construct(BasicTOCNavigatorUI.java:252)
        at com.sun.java.help.impl.SwingWorker$2.run(SwingWorker.java:129)
        at java.lang.Thread.run(Thread.java:595)

A window opens, but unfortunately without content.  Everything is
fine with English ISO-8859-1 source.  I use the following software:

ii  docbook-xml    4.3-1.1        standard XML documentation system, for softw
ii  docbook-xsl    1.68.1-0.1     stylesheets for processing DocBook XML files
ii  xsltproc       1.1.12-8       XSLT command line processor

Many thanks in advance for any hint!

Cheers, W. Borgert