membership add on - cannot seem to be able to logoff

Hello,
I was having a go with the membership add on, whilst it works, it is when it comes to loging out that I am having issuers with.

http://www.mysitename.com/

I have added this to the index.php page centre 

<p>hi thanks for the help - start </p>

<p>
<?php if ($CURRENT_USER): ?>
<a href='index.php?action=logoff'>Logoff</a>
<?php endif ?>
</p>
<p>thanks for the help finish</p>

when a punter is logged in and clicks that logoff link, they still not logged out, as when I go to

http://www.mysitename.com/user-login.php

It states I am still logged in

please note I have given this a go prior to emailing you but that didn't do it for me

http://www.interactivetools.com/forum/forum-posts.php?postNum=2236009#post2236009

grateful for any input

kenny