How to get on with luxor.swing.tree?

  Hi, 

I was glad to find Luxor Swing libraries! Namely, I was interested in XmlTreeModel to use in my tool GUI. 
I have never used Luxor before, so I'm sorry for stupid questions in advance:) 

In my tool I'd like to have a swing tree constructed over a concret XML document (not DTD) 
then I use TreeSelectionListener from javax.swing.tree 
and have a java.lang.ClassCastException 

that's what I do in my code: 
// this is just for converting org.w3c.dom.Document 
// into org.jdom.Document for use in XmlTreeModel 
// (maybe it's not right? help!) 

org.jdom.input.DOMBuilder domBuilder = new org.jdom.input.DOMBuilder(); 

org.jdom.Document docJdom = domBuilder.build(doc); 

XmlTreeModel treeModel = new XmlTreeModel(docJdom); 

//Create a tree that allows one selection at a time. 
tree = new JTree(treeModel); 
tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION); 

//Listen for when the selection changes. 
tree.addTreeSelectionListener(new TreeSelectionListener() { 
                       public void valueChanged(TreeSelectionEvent e) { 
                               DefaultMutableTreeNode node = (DefaultMutableTreeNode) tree.getLastSelectedPathComponent(); 

                                       if (node == null) return; 

                                       Object nodeInfo = node.getUserObject(); 
                                        if (node.isLeaf()) { 
                                        System.out.println(" Leaf!! "); 
                                                                                                       }   
                        } 
   }); 

so I have an Exception at line with tree.getLastSelectedPathComponent(); 

What should I do?