URL masking problem

[jpn]

I have a domain name lets say www.fake.com.

This address gets forwarded to lets say www.real.com

When I try and login at www.fake.com (URL masking enabled) It won't let me in; howeverwhen I disable URL masking I can login without any problems.

I really need to mask the URL as I dont want the real domain name appearing. Any ideas on what could be causing this?

Here is the login form code:

<form action="cgi-bin/checkuser.php" method="post">
<table width="30%" border="0">
   <tr>
      <td colspan = "2">&nbsp;</td>
   </tr>
   <tr>
      <td><span class = "bodytext">Username</span></td>
      <td><input name="username" type="text" size="7" maxlength="7"></td>
   </tr>
   <tr>
      <td><span class = "bodytext">Password</span></td>
      <td><input name="password" type="password" size="7" maxlength="7"></td>
   </tr>
   <tr>
      <td>&nbsp;</td>
      <td><input name="login" type="submit" value="Log-in"></td>
   </tr>
</table>
</form>

Here is code that checks login Info:

<?

// Convert to simple variables
$username = $_POST['username'];
$password = $_POST['password'];

if((!$username) || (!$password)){
	 header("Location: ../login.html");
	 exit();
}

require ('mysql_connect.php');	//connect to the db

// check if the user info validates the db
$sql = mysql_query("SELECT * FROM ffaControl WHERE username='$username' AND password='$password'");
$login_check = mysql_num_rows($sql);

if($login_check > 0){
    while($row = mysql_fetch_array($sql)){
    foreach( $row AS $key => $val ){
        $$key = stripslashes( $val );
    }
        // Register a session variable
		session_register('username');
        $_SESSION['userID'] = $username;
		mysql_close(); // Close the database connection.
		header("Location: ../vessels.php");
    }
} else {
      header("Location: ../login.html");
	  exit();
}
?>

If a login is successful then it will take me to vessels.php at the top of which is the following code (ensuring that user has logged in)

<?
session_start();
include '../cgi-bin/sessionchecker.php';
session_checker();
?>

I suspect that the problem lies because I am using sessions but I can't be sure. Is there a workaround I could use?

Thanks in advance,

John