Cannot populate a xul tree from XML

Hello,
I am trying to populate a xul tree from an XML document.

I am using the "@mozilla.org/inspector/dom-view;1" component.

The xul tree load the XML document structure correctly: I can see the 
"+" in the right place, but the problem is that no label is displayed at 
all.

I just have a correct but completely anonymous XML structure.

Here is my code:

*****************

var domView = 
Components.classes["@mozilla.org/inspector/dom-view;1"].createInstance(Components.interfaces.inIDOMView);

var domDocument = document.implementation.createDocument("", "", null);
domDocument.load('chrome://crawlermodelgen/content/morningstar.xml');

domView.rootNode = domDocument;
domView.showWhitespaceNodes = true;
domView.showAnonymousContent = true;
domView.showSubDocuments = true;
domView.whatToShow &= (NodeFilter.SHOW_ALL);

var sidebarTree = sidebar.document.getElementById("cmgDOMTree");
sidebarTreeBox.view = domView;

*****************

What do I do wrong? Is this the right way to face this issue?

Luca