newbie: DTMDOMException in xalan Extension

[Christopher Giblin]

Hi

I can't figure out why I always get:

org.apache.xml.dtm.DTMDOMException:
        at
org.apache.xml.dtm.ref.DTMNodeProxy.createTextNode(DTMNodeProxy.java:617)

My code is so simple, I must be overlooking something obvious.
Java source and stylesheet given below.
xalan 2.2.D13 plus bundled xerces (1.4.3, I believe). JDK 1.4 beta 3
Grateful for any any pointers
Thanks, chris

public static NodeSet nextMatch(ExpressionContext myContext, String junk) {
    Document lDoc = myContext.getContextNode().getOwnerDocument();
    if (lDoc == null) {
     System.err.println("null doc!!!");
     return null;
    }
    NodeSet resultSet = new NodeSet();
     Node node = lDoc.createTextNode("xx");
    System.err.println("created node");
    resultSet.addNode(node);
   return resultSet;

My stylesheet:

<?xml version="1.0"?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
                xmlns:lxslt="http://xml.apache.org/xslt";
                xmlns:regex="test"
                extension-element-prefixes="regex test"
                version="1.0">

<lxslt:component prefix="test"
           functions="nextMatch">
    <lxslt:script lang="javaclass"  src="xalan://com.test..MyExtension"/>
</lxslt:component>

<xsl:template match="//[EMAIL PROTECTED]'IP Address']">
   <ipaddr>
     <xsl:value-of select="test:nextMatch('junk')"/>
   </ipaddr>
</xsl:template>

</xsl:stylesheet>