XOM XInclude: relative URIs on OS X vs. Windows

I'm using XMLShell, which uses XOM, to process xincludes for a document.

It works flawlessly on OS X.

On Windows, I get
"Exception running: xinclude nu.xom.xinclude.BadHrefAttributeException: 
Could not resolve relative URI 
../User_Guide/Module_Details/persistance.xml because the xi:include 
element does not have a base URI."

Is there something special about Windows that it needs a base uri?

<xi:include href="../User_Guide/Module_Details/persistance.xml" 
xpointer="element(/1)"/>

I have tried setting an xml:base reset (xml:base="") and tried setting 
hard paths (xml:base="C:\Users\davidp\home\doc-source\One-Sheets\").  
XOM is unhappy in all cases.

Any hints on what to do next?  I'm quite baffled why XOM would perform 
differently on OS X versus Windows.

Thanks in advance
   david