Session/Cookie Login

[klik]

Okay, I have a cookie set and a session set to hold the username of the user.

At the top of the page I have:

<?php


if(isset($_COOKIE["hhr_account"])){
	$username = $hhr_account;

	$sql = mysql_query("SELECT * FROM cms_users WHERE username='$username'");
	$login_check = mysql_num_rows($sql);

	if($login_check > 0){
		$_SESSION["username"] = $username;

		/* Update last login date */
		mysql_query("UPDATE cms_users SET last_login=now() WHERE username='$username'");
		/* END Update last login date */

		/* Method to only update points on a per hour basis */
    		mysql_query("UPDATE cms_users SET user_points = user_points+1 WHERE username= '$username' AND  point_interval < NOW()- 3600");
    		mysql_query("UPDATE cms_users SET point_interval = now() WHERE username='$username'");
		/* END Method to only update points on a per hour basis */
	}

}


if(isset($_SESSION["username"])){

	$username = $_SESSION["username"];
	stripslashes($username);
	$data = $username;
	setcookie("hhr_account","$data",time()[phone]);
}



if ($_GET['action'] == "logout"){

	/* set the expiration date to one hour ago */

	session_unregister("username");
	session_unregister("registered");
	session_unset();
	session_destroy();
	setcookie ("hhr_account", "", time() - 3600, "/");

header("Location: /index.php");
}



/* ...................................................................................... */

?>

Then to display whether they are logged in or not I use the following:

<?php


if (isset($_POST['submit_x']))
{
	login_results();
}

if (isset($_SESSION["username"])){

	$username = $_SESSION["username"];	
	$user_level = mysql_query("SELECT user_level FROM cms_users WHERE username = '$username'");
	$user_level = mysql_result($user_level, 0);
	$avatar = mysql_query("SELECT avatar FROM cms_users WHERE username = '$username'");
	$avatar = mysql_result($avatar, 0);

	$pm_query = mysql_query("SELECT * FROM cms_privatemessage WHERE userto='{$_SESSION["username"]}' AND status='0' AND opened='0'");
	$new_pm_count = mysql_num_rows($pm_query);

	$ft_query = mysql_query("SELECT * FROM cms_freshtalent WHERE freshtalent_user = '{$_SESSION["username"]}'");
	$ft_count = mysql_num_rows($ft_query);

echo'
<table width="568" border="0" cellpadding="0" cellspacing="0">
  <tr> 
    <td width="192" height="33" bgcolor="#FFFFFF"> 
      <div align="left"><font color="#000000">
	  Welcome </font><font color="#FF3300">' . $_SESSION["username"] . '</font></div>
    </td>
    <td width="187" height="33" bgcolor="#FFFFFF">
';

  if($new_pm_count == 1){
  	echo' <font class="redlinks"><a href="/pm/">You have <strong>' . $new_pm_count . '</strong> unread PM</a></font>';
  }
  else if($new_pm_count > 1){
  	echo' <font class="redlinks"><a href="/pm/">You have <strong>' . $new_pm_count . '</strong> unread PM\'s</a></font>';
  }
  else{
  	echo' <a href="/pm/">You have no unread PM\'s</a>';
  }


echo'
	 </td>
    <td width="53" height="33" bgcolor="#FFFFFF"> 
      <div align="center"><b> </b></div>
    </td>
    <td width="240" height="33" bgcolor="#FFFFFF"> 
      <div align="right">';
	  if($ft_count != 0){
	  	echo'<b><a href="/freshtalent/editpage.php">Edit Talent</a></b> |';
	  }

echo'
		<b><a href="/edit_profile.php">Edit profile</a></b> | 
        <a href="?action=logout">Logout</a>&nbsp;&nbsp;</div>
    </td>
  </tr>
</table>
';
}
else
{
	login_form();
}
?>

The problem here being that I cannot logout. Where have I gone wrong?

Thanks!