This has actually occured since Joomla 1.6 and has carried forward to Joomla 1.7.  In Joomla 1.6 and Joomla 1.7 they have added a token on logout therefore causing problems when registered users are logging out of your website.The error message is:

Invalid Token

The solution is to add a token to the default.php file in the template overrides for the mod_login.  Steps to do this is below:

1.  Login to your FTP manager or file manager in you webhosting cpanel

2.  Go to your default template directory, for example:

templates/Beez_20/html/mod_login/default.php

3.  Find the following code:

<div>
<input type=”submit” name=”Submit” value=”<?php echo JText::_(‘JLOGOUT’); ?>” />
</div>

4.  Replace the code with:

<div>
<?php echo JHtml::_(‘form.token’); ?>
<input type=”submit” name=”Submit” value=”<?php echo JText::_(‘JLOGOUT’); ?>” />
</div>

5.  Save the file.

Refresh your website and test the logout function.  You should not have any problems.

Thanks,

Elaine