conversation is lost

[aatsy]

hi I am using icefaces with seam , I have bean with convesation scope and page have test button

@Name("colorLookupBean")
@Scope(ScopeType.CONVERSATION)
public class ColorLookupBean implements Serializable {

        @Begin(join = true)
        public void test(ActionEvent evt) {
                System.out.println("ColorLookupBean.test()");
        }

}

the button

<ice:commandButton value="#{conversation.id}" actionListener="#{colorLookupBean.test}"/>

when i click this button first and second time succefully run and the third throw exception
SEVERE: javax.el.PropertyNotFoundException: /jsp/base/TestColorLookupList.jsp @30,92 actionListener="#{colorLookupBean.test}": Target Unreachable, identifier 'colorLookupBean' resolved to null__