Problems with Jahia JForum 2.x

Hi list!

I have a problem with this portlet because when i login like Admin, it 
don't recognize the session and don't show me the link to Admin control 
panel.
I know this because into the file: /templates/default/header.htm I put 
one IF before: 

<#if session?exists && session.isAdmin()>
                                                                                  
<a id="adminpanel" class="mainmenu" style="clore:red;" 
href='${JForumContext.encodeURL("/admBase/login")}'><img 
src="${contextPath}/templates/${templateName}/images/icon_mini_login.gif" 
border="0"/>${I18n.getMessage("ForumBase.admin")}</a>
                                                                                
</#if>

If i put another If before like:  <#if session?exists>Say Hello</if> it 
show me the message, but if i put something like: <#if 
session.isAdmin()>Say Hello</if> it doesn't work.

Can you help me?

Thank you!

Adolfo.