Vil ikke rette password

Hej

Jeg har denne kode til at kunne rette sit password med:

<?php
session_start();
include('config.php');
$id=intval($_GET['id']);
if(!$_SESSION['logget_ind'] == "1") {
header('Location: /login.php');
exit;
}
$nick=$_SESSION['user'];
$old_password = mysql_escape_string($_POST['old_password']);
$new_password = mysql_escape_string($_POST['new_password']);
$new_password2 = mysql_escape_string($_POST['new_password2']);

$resultat = mysql_query("SELECT id FROM brugere WHERE nick = '$nick' AND password=MD5('$old_password')");
$row = mysql_fetch_array($resultat);
$number=mysql_num_rows($resultat);

if (empty($old_password) OR empty($new_password) OR empty($new_password2)) {
    require_once('topbar.php');
    echo '<div align="center"><center><table border="0" width="744" cellspacing="0" cellpadding="2" style="border: 1px solid #000000"><tr><td width="100%" bgcolor="#B9E1FD">';
    echo '<font face="verdana" style="font-size: 11px;"><b>Du skal udfylde alle felterne.</b><br><a href="java script:history.go(-1)">Tilbage</a>';
    echo '</td></tr></table></center></div>';
} elseif ($new_password != $new_password2) {
    require_once('topbar.php');
    echo '<div align="center"><center><table border="0" width="744" cellspacing="0" cellpadding="2" style="border: 1px solid #000000"><tr><td width="100%" bgcolor="#B9E1FD">';
    echo '<font face="verdana" style="font-size: 11px;"><b>Password og Gentag Password er ikke ens.</b><br><a href="java script:history.go(-1)">Tilbage</a>';
    echo '</td></tr></table></center></div>';
} elseif ($number == 0) {
    require_once('topbar.php');
    echo '<div align="center"><center><table border="0" width="744" cellspacing="0" cellpadding="2" style="border: 1px solid #000000"><tr><td width="100%" bgcolor="#B9E1FD">';
    echo '<font face="verdana" style="font-size: 11px;"><b>Du har skrevet forkert!</b><br><a href="java script:history.go(-1)">Tilbage</a>';
    echo '</td></tr></table></center></div>';
} else {
    if($number == 1)
    {
        mysql_query("UPDATE brugere SET password=MD5('$new_password') WHERE nick='$nick'") or die (mysql_error());
       
        $nick = $_COOKIE['nick'];
        $password = $_COOKIE['password'];

        if (isset($nick) && isset($password))
    {
        setcookie("nick", "", time()-31536000);
        setcookie("password", "", time()-31536000);
        $_LOGOUT = true;
    }
    }
}
?>


Kode virker 100% men hvis brugerne har valgt auto login (cookie) Så vil den ikke rette passwordet den skriver bare "Du har skrevet forkert!".

Nogle der kan hjælpe mig?