session_regerate_id() issue

[Wolfsbane]

I get the following error when I run an authentication script:

PHP Warning: session_regenerate_id() [/etc/php5/helpdocs/htmlfunction.session-regenerate-id.html]: Session object destruction failed in /srv/www/htdocs/PEAR/Auth.php on line 830, referer: http://homeserver/recipe/index.php

This error does not happen every time just every other time. I can log in and get the error then log out and then log back in and not get the error the repeat the process and get the error. I have checked permissions on the session directory and they are fine.

The first page (index.php):
<?php
require_once('config.php');
$smarty->assign('web_title',$web_title);
$smarty->display('header.tpl');
?>
<form action="login.php">
<input type="submit" value="Login in"/>
<br>
<br>
</form>
<form method="link" action="register.php">
<input type="submit" value="New user">
</form>
</body>

The index page sends you to this (login.php):

<?php

// Example of Auth_HTTP the also returns additional information about the user thank you to Michele Davis and Jon A. Phillips
// Learning PHP & MySQL - O'REILLY Media.
require_once('config.php');
require_once('db_login.php');
require_once('Auth/HTTP.php');
// require_once('Log.php');
// error_log(PEAR_LOG_TYPE_DEBUG);
$AuthOptions = array(
'dsn'=>"mysql://$db_username:$db_password@$db_host/$db_database",
'table'=>"users",
'usernamecol'=>"username",
'passwordcol'=>"password",
'cryptType'=>"md5",
'db_fields'=>"*"
);
$authenticate = new Auth_HTTP("MDB2", $AuthOptions);
$authenticate->setRealm('Member Area');
$authenticate->setCancelText('<h2>Access Denied</h2>');

$authenticate->start( );
if ($authenticate->getAuth( )) {
session_start( );
header("Cache-control: private");
$smarty->assign('web_title',$web_title);
$smarty->display('header.tpl');
//setup session variable
echo '<meta http-equiv="refresh" content="4; url=mainmenu.php">';
$_SESSION['username'] = $authenticate->username;
$_SESSION['first_name'] = $authenticate->getAuthData('first_name');
$_SESSION['last_name'] = $authenticate->getAuthData('last_name');
$_SESSION['user_id'] = $authenticate->getAuthData('user_id');
echo "Login successful. Great to see you ";
echo $authenticate->getAuthData('first_name');
echo " ";
echo $authenticate->getAuthData('last_name').".<br />";
//$smarty->display('footer.tpl');
}
?>

This page contains the first session_start() statement and like I said bombs every other time.