Experienced the problem on:
Windows XP with sun JDK 1.6.0_20
Redhat Linux 5.4 with jdk 1.6.0_16-b01
Note:
I am trying to use XmlUtil directly, as a utility. I was not using it via the BPM Engine. This is probably why the default implementation of org.w3c.dom.Node (i.e com.sun.org.apache.xerces.internal.dom.NodeImpl) gets used. I did use it successfully with jBPM 4.3
I have subsequently created my own XmlParserUtility, so this is not a major issue at this time.
I will attempt to build jbpm 4 from source. I have never done this before.