on mac os x there is a null pointer if you call getLength() on an empty node list, so add a second check there (hope this helps ... but I doubt it).

src/net/java/sip/communicator/util/xml/DOMElementWriter.java

@@ -111,7 +111,11 @@ public void write(Node element, Writer out, int indent,
         // Write child elements and text
         boolean hasChildren = false;
         NodeList children = element.getChildNodes();
-        for (int i = 0; i < children.getLength(); i++) {
+        for (int i = 0
+             ; element.hasChildNodes()
+               && i < children.getLength()
+             ; i++)
+        {
             Node child = children.item(i);
 
             switch (child.getNodeType()) {