error login

[servidigital]

mira este es el codigo que tengo para el login

Código PHP:

<?php
// *** Validate request to login to this site.
if (!isset($_SESSION)) {
  session_start();
}
 
$loginFormAction = $_SERVER['PHP_SELF'];
if (isset($_GET['accesscheck'])) {
  $_SESSION['PrevUrl'] = $_GET['accesscheck'];
}
 
if (isset($_POST['log'])) {
  $loginUsername=$_POST['log'];
  $password=$_POST['pwd'];
  $MM_fldUserAuthorization = "admin_priv";
  $MM_redirectLoginSuccess = "jimdvd.html";
  $MM_redirectLoginFailed = "index.php";
  $MM_redirecttoReferrer = false;
  mysql_select_db($database_jimdvd, $jimdvd);
    
  $LoginRS__query=sprintf("SELECT usuario, pass, admin_priv FROM usuarios WHERE usuario=%s AND pass=%s",
  GetSQLValueString($loginUsername, "text"), GetSQLValueString($password, "text")); 
   
  $LoginRS = mysql_query($LoginRS__query, $jimdvd) or die(mysql_error());
  $loginFoundUser = mysql_num_rows($LoginRS);
  if ($loginFoundUser) {
    
    $loginStrGroup  = mysql_result($LoginRS,0,'admin_priv');
    
    if (PHP_VERSION >= 5.1) {session_regenerate_id(true);} else {session_regenerate_id();}
    //declare two session variables and assign them
    $_SESSION['MM_Username'] = $loginUsername;
    $_SESSION['MM_UserGroup'] = $loginStrGroup;       
 
    if (isset($_SESSION['PrevUrl']) && false) {
      $MM_redirectLoginSuccess = $_SESSION['PrevUrl'];  
    }
    header("Location: " . $MM_redirectLoginSuccess );
  }
  else {
    header("Location: ". $MM_redirectLoginFailed );
  }
}
?>