MySQL Error

[Sorry for bad English.]

My hotel got an error. It cause at C:\xampp\htdocs\client/disconnected.php

This is the warning error

Code:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in C:\xampp\htdocs\client\disconnected.php on line 10

My disconnect.php file

Code:

<?phpsession_start(); include("../config.php"); if(!isset($_SESSION["username"])) header("Location: ../characters.php"); elseif(!isset($_SESSION["account"])) header("Location: ../index.php"); $username = $_SESSION['username']; $ban = mysql_query("SELECT * FROM bans WHERE bantype = 'user' AND value ='".$username."' AND expire > ".time().""); if(mysql_num_rows($ban) > 0) { session_destroy(); header("Location: index.php?error=ban"); die; } ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <link type="text/css" rel="stylesheet" href="../Public/Styles/<?php echo $currentstyle ?>/CSS/main.css" /> </head> <body style="text-align:center"> <table style="padding:50px 50px 50px 50px;"> <tr> <td width="30%"></td> <td style="width:64px; height:64px; background-image:url(/Public/Styles/Default/Images/icons/warning_64.png); background-repeat:no-repeat"></td> <td style="width:400px"> <strong>A problem occurred, sorry!</strong><br/> Please try reloading the hotel, if the problem continues wait a few minutes before trying again. If you are unable to get onto the hotel for a long peroid of time please report the issue on our forums. </td> <td width="30%"></td> </tr> </table> <?php include("../system/footer.php"); ?> </body>