RDF Tree problem

Hi,
I'm having a problem building a tree from an RDF datasource. The
following XUL creates both a tree and a listbox with the same local
datasource. The listbox works fine, but the tree appears with the
second column the same as the first - and if I add more columns, they
all appear the same as the first.
Now I'm sure I had this working a while ago, but I just can't find
anything wrong with it. Any ideas?

If you want to try the full extension, it's at
http://peteburgers.fastmail.fm/rdf/rdftest.xpi

Thanks
Pete

XUL))))))))))))))))))))))))))))))))))))))))))))))))
<?xml version="1.0"?>

<window

    id="RDFTest-window"


xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">

    <vbox flex="1">



<!-- Listbox: works fine (rows are: a 1, b 2, c 3)-->

        <listbox id="UpdateList" flex="1"
datasources="file:///c|/updatescan.rdf"

                 ref="http://www.updatescan.com/rdf/updatescan/all">

            <listcols>

                <listcol flex="1"/>

                <listcol flex="1"/>

            </listcols>

            <listhead>

                <listheader label="letters"/>

                <listheader label="numbers"/>

            </listhead>



            <template>

                <listitem uri="rdf:*">

                    <listcell
label="rdf:http://www.updatescan.com/rdf/updatescan#letters"/>

                    <listcell
label="rdf:http://www.updatescan.com/rdf/updatescan#numbers"/>

                </listitem>

            </template>

        </listbox>



<!-- Tree: second column is same as first column (rows are: a a, b b, c
c)-->

        <tree id="UpdateList2" flex="1"
datasources="file:///c|/updatescan.rdf"

                 ref="http://www.updatescan.com/rdf/updatescan/all">

            <treecols>

                <treecol label="letters" flex="1"/>

                <treecol label="numbers" flex="1"/>

            </treecols>

            <template>

                <treechildren>

                    <treeitem uri="rdf:*">

                        <treerow>

                            <treecell
label="rdf:http://www.updatescan.com/rdf/updatescan#letters"/>

                            <treecell
label="rdf:http://www.updatescan.com/rdf/updatescan#numbers"/>

                        </treerow>

                    </treeitem>

                </treechildren>

            </template>

        </tree>

    </vbox>

</window>

RDF))))))))))))))))))))))))))))))))))))))))))))))))
<?xml version="1.0"?>
<RDF:RDF xmlns:NS2="http://www.updatescan.com/rdf/updatescan#"
         xmlns:NC="http://home.netscape.com/NC-rdf#"
         xmlns:RDF="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <RDF:Seq RDF:about="http://www.updatescan.com/rdf/updatescan/all">
    <RDF:li RDF:resource="http://test.com/1"/>
    <RDF:li RDF:resource="http://test.com/2"/>
    <RDF:li RDF:resource="http://test.com/3"/>
  </RDF:Seq>

  <RDF:Description RDF:about="http://test.com/1"
                   NS2:letters="a"
                   NS2:numbers="1"
    />
  <RDF:Description RDF:about="http://test.com/2"
                   NS2:letters="b"
                   NS2:numbers="2"
    />
  <RDF:Description RDF:about="http://test.com/3"
                   NS2:letters="c"
                   NS2:numbers="3"
    />
</RDF:RDF>