Docbook Webhelp: saxparser problem

[David Priest <docs@davidpriest.ca>]

I've been trying to implement in Ant the indexer part of the Docbook 
Webhelp transformation.  I have this error:
[major snippage]
      [xslt] JAXP: find factoryId =javax.xml.parsers.SAXParserFactory
      [xslt] JAXP: loaded from fallback value: 
com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl
      [xslt] JAXP: created new instance of class 
com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl using 
ClassLoader: null
      [echo] Indexing html files in 
/Users/davidp/dev/release-docs/Admin_Guide-webhelp/content
[indexertask] JAXP: find factoryId =javax.xml.parsers.SAXParserFactory
[indexertask] JAXP: found system property, 
value=org.apache.xerces.jaxp.SAXParserFactoryImpl

BUILD FAILED
/Users/davidp/dev/davidpriest/ant/publish.xml:420: 
javax.xml.parsers.FactoryConfigurationError: Provider 
org.apache.xerces.jaxp.SAXParserFactoryImpl not found
     at 
javax.xml.parsers.SAXParserFactory.newInstance(SAXParserFactory.java:134)
     at 
com.nexwave.nquindexer.SaxDocFileParser.parseDocument(SaxDocFileParser.java:67)
[snip]

There are a nigh-infinite number of debug messages where JAXP loads from 
fallback.  And *immediately* before the indexer is fired-up, JAXP does 
exactly the same thing as had worked for every other step of the 
transformation process.

But then, whack, nquindexer craps out when it tries to execute its 
indexer task.

I have tried to point it directly at xerces by including it in the 
indexer's classpath.  I've tried eliminating classes that I think might 
contain a sax parser of their own (but, then, if those were interfering, 
I'd expect the other debug messages to indicate that).

I should note that my Ant indexertask is copied directly from the script 
provided with Docbook's Webhelp.

Does anyone have any hints on how I can resolve this issue?

Thanks in advance
   david