How to programmatically reRender a component

[balteo]

Hello,
I am having big problem reRendering an ajax component: see thread:
http://jboss.com/index.html?module=bb&op=viewtopic&t=140231

I am now trying to reRender it programmatically as follows with an ajaxListener:

public class CaptchaAjaxListener implements AjaxListener {
 private static transient Logger log = Logger.getLogger("com.jeanbaptistemartin.util");

 @Override
 public void processAjax(AjaxEvent event) {
 log.info("processAjax");
 UIComponent comp = event.getComponent();
 UIComponent component = comp.findComponent("captchaImage");
 log.info("getClientId: "+component.getClientId(FacesContext.getCurrentInstance()));
 AjaxRenderEvent renderEvent = new AjaxRenderEvent(component);
 renderEvent.setPhaseId(event.getPhaseId());
 log.info("getPhaseId: "+ event.getPhaseId());
 component.queueEvent(renderEvent);
 }
}

<a4j:commandButton value="#{msg['message.envoyer']}" action="#{contactView.envoyer}" reRender="wrapper,captchaImage" >
 <a4j:ajaxListener type="com.jeanbaptistemartin.util.CaptchaAjaxListener"/>
 </a4j:commandButton>

Even that fails.

How can I make sure my captcha is reRender regardless of whether the request is an ajax request or a plain http request?

Thanks in advance,

Julien.