Smarty & Rickard - Thanks for all the help...  Much appreciated.  I'll be rolling out the site soon.

Here is the check_cookie function:

function check_cookie(&$pun_user)
{
    global $db, $pun_config, $cookie_name, $cookie_seed;

    $now = time();
    $expire = $now + 31536000;    // The cookie expires after a year

    // We assume it's a guest
    $cookie = array('user_id' => 1, 'password_hash' => 'Guest');

    // If a cookie is set, we get the user_id and password hash from it
    if (isset($_COOKIE[$cookie_name]))
        list($cookie['user_id'], $cookie['password_hash']) = @unserialize($_COOKIE[$cookie_name]);

    if ($cookie['user_id'] > 1)
    {
        // Check if there's a user with the user ID and password hash from the cookie
        $result = $db->query('SELECT u.*, g.*, o.logged, o.idle FROM '.$db->prefix.'users AS u INNER JOIN '.$db->prefix.'groups AS g ON u.group_id=g.g_id LEFT JOIN '.$db->prefix.'online AS o ON o.user_id=u.id WHERE u.id='.intval($cookie['user_id'])) or error('Unable to fetch user information', __FILE__, __LINE__, $db->error());
        $pun_user = $db->fetch_assoc($result);

        // If user authorisation failed
        if (!isset($pun_user['id']) || md5($cookie_seed.$pun_user['password']) !== $cookie['password_hash'])
        {
            pun_setcookie(0, random_pass(8), $expire);
            set_default_user();

            return;
        }

        // Set a default language if the user selected language no longer exists
        if (!@file_exists(PUN_ROOT.'lang/'.$pun_user['language']))
            $pun_user['language'] = $pun_config['o_default_lang'];

        // Set a default style if the user selected style no longer exists
        if (!@file_exists(PUN_ROOT.'style/'.$pun_user['style'].'.css'))
            $pun_user['style'] = $pun_config['o_default_style'];

        if (!$pun_user['disp_topics'])
            $pun_user['disp_topics'] = $pun_config['o_disp_topics_default'];
        if (!$pun_user['disp_posts'])
            $pun_user['disp_posts'] = $pun_config['o_disp_posts_default'];

        if ($pun_user['save_pass'] == '0')
            $expire = 0;

        // Define this if you want this visit to affect the online list and the users last visit data
        if (!defined('PUN_QUIET_VISIT'))
        {
            // Update the online list
            if (!$pun_user['logged'])
                $db->query('INSERT INTO '.$db->prefix.'online (user_id, ident, logged) VALUES('.$pun_user['id'].', \''.$db->escape($pun_user['username']).'\', '.$now.')') or error('Unable to insert into online list', __FILE__, __LINE__, $db->error());
            else
            {
                // Special case: We've timed out, but no other user has browsed the forums since we timed out
                if ($pun_user['logged'] < ($now-$pun_config['o_timeout_visit']))
                {
                    $db->query('UPDATE '.$db->prefix.'users SET last_visit='.$pun_user['logged'].' WHERE id='.$pun_user['id']) or error('Unable to update user visit data', __FILE__, __LINE__, $db->error());
                    $pun_user['last_visit'] = $pun_user['logged'];
                }

                $idle_sql = ($pun_user['idle'] == '1') ? ', idle=0' : '';
                $db->query('UPDATE '.$db->prefix.'online SET logged='.$now.$idle_sql.' WHERE user_id='.$pun_user['id']) or error('Unable to update online list', __FILE__, __LINE__, $db->error());
            }
        }

        $pun_user['is_guest'] = false;
    }
    else
        set_default_user();
}

******************************************************
Also, I have included the setcookie function (just to make sure) since I uncommented the P3P section:

function pun_setcookie($user_id, $password_hash, $expire)
{
    global $cookie_name, $cookie_path, $cookie_domain, $cookie_secure, $cookie_seed;

    // Enable sending of a P3P header by removing // from the following line (try this if login is failing in IE6)
    @header('P3P: CP="CUR ADM"');

    setcookie($cookie_name, serialize(array($user_id, md5($cookie_seed.$password_hash))), $expire, $cookie_path, $cookie_domain, $cookie_secure);
}

I tried a few variations for $cookie_domain and none seemed to work:

.grupofantasma.com
grupofantasma.com
www.grupofantasma.com
grupofantasma
.grupofantasma

Also, the cookie path is:  $cookie_path = '/';

Is this possibly related to the unregister_globals function being commented out?

Thanks so much for your help...  Hope I can get this worked out soon...

Nope...  not that I am aware of at least.

Hello...

I have set up a new forum and am having the login issue that many other people have mentioned where a user logs in successfully, is redirected back to the main page, but then is not actually logged in.  This seems to be happening for a number of users, in both Firefox and IE.  It was working successfully for a week or so before this behavior started.  Here is what I have tried so far:

1.  Clear cache
2.  Clear cookies
3.  Uncomment the P3P line in functions.php
4.  Reupload login.php
5.  Check $cookie_domain = ''

Also, I have commented out the unregister_globals function to allow for some other site functionality.  As far as I know, it was still working after that.

You can view the site here:  http://www.grupofantasma.com/forum/index.php

Thanks for your help,

Adam