a4j re-rendering

Hi all,

I have a list of controls dynamically created and need to re-render 
their content at some events.
For example the next piece of code generates several listboxes and fill 
with data from a directory source.
The idea is that when the user clicks on an item from a list box the 
others to be reloaded.

    <ui:repeat value="#{directories}" var="data">
       <nxdir:chainSelectListbox
           id="themex"
           index="#{data.index}"
           size="4"
           directoryName="#{data.dirName}"
           displayObsoleteEntries="true"
           displayIdAndLabel="false"
       >

         <a4j:support event="onchange" reRender="themex" >
           <a4j:ajaxListener type="org.ajax4jsf.ajax.ForceRender" />
         </a4j:support>

       </nxdir:chainSelectListbox>

    </ui:repeat>

What happens now is that only the first generated control is being 
re-rendered.
Any suggestion appreciated.

Thanks,
Dragos