membership tutorial

hi
i'm trying to get the membership tutorial on this site to work.
what the problem is when i register i get the email. i click the activate link, but it doesn't activate. where could the problem be

Your account could not be activated!
below is the activate.php

<?
include 'db.private';
$connection = mysql_connect($hostname,$username,$password);
mysql_select_db($databaseName, $connection);
$userid = $_REQUEST['id'];
$code = $_REQUEST['code'];
$sql = mysql_query("UPDATE users SET activated='1' WHERE userid='$userid' AND password='$code'");
$sql_doublecheck = mysql_query("SELECT * FROM users WHERE userid='$userid' AND password='$code' AND activated='1'");
$doublecheck = mysql_num_rows($sql_doublecheck);
if($doublecheck == 0){
echo "<strong><font color=red>Your account could not be activated!</font></strong>";
} elseif ($doublecheck > 0) {
echo "<strong>Your account has been activated!</strong> You may login below!<br />";
include 'login_form.html';
}
?>

thanks