Xerces' TreeWalker - og dispatachChars?!

Det her ser fuldstændig sort ud for mig:

Koden:
        DOMSource source = new DOMSource( doc);
        StreamResult result = new StreamResult( writer);
        transformer.transform( source, result);

Fejlen:
java.lang.NullPointerException: null
    at org.apache.xml.utils.TreeWalker.dispatachChars(TreeWalker.java:292)
    at org.apache.xml.utils.TreeWalker.startNode(TreeWalker.java:436)
    at org.apache.xml.utils.TreeWalker.traverse(TreeWalker.java:191)
    at org.apache.xalan.transformer.TransformerIdentityImpl.transform(TransformerIdentityImpl.java:325)
...