cannot access method using seam and ejb3

[margas]

Hi,
I have a sample application (seam-ejb3-richfaces).
In one page i want to use <rich:tabPanel> and a valueChangeListener so that to get events when i change tabs.
It seems that the valueChangeListener fires the events but when it tries to execute the method i get the following warning.

WARN [lifecycle] /projecttype.xhtml @73,90 valueChangeListener="#{projecttype.changeTab}": Method not found: TProjecttypeAction:a00a-2idpbn-f71lr7w3-1-f71ls2aq-a.changeTab()

I post some code that can help :

Interface

@Local
public interface TProjecttypeInt {


 String changeTab(ValueChangeEvent evtHandle);

Session Bean

@Stateful
@Name("projecttype")
@Scope (SESSION)
@Restrict("#{identity.loggedIn}")
public class TProjecttypeAction extends Search implements TProjecttypeInt{

 public String changeTab(ValueChangeEvent evtHandle){
 if (!evtHandle.getOldValue().toString().trim().equalsIgnoreCase("edit")){
 if (currentPknId !=null && !currentPknId.trim().equalsIgnoreCase("")){
 pknId = Integer.valueOf(currentPknId);
 tProjecttype = em.find(TProjecttype.class, Integer.valueOf(currentPknId));
 }
 }
 tabName = evtHandle.getNewValue().toString();
 return "/projecttype.xhtml";
 }

Page

<rich:tabPanel selectedTab="#{tabName}" valueChangeListener="#{projecttype.changeTab}">

I cannot figure out why this happens if someone can give a hint
thank you