Okay, well I'm having problems with my simple, yet nice, login script

See, I don't know why it's not working, it just stopped for some reason, not sure why. I've asked around and they don't know what to say either, so here I am, and heres the code some of you have already seen, again
[code:1:838babf581]<? session_start(); ?>
<?php
include("config.php");
$connect = mysql_connect("$user_hostname", "$user_username", "$user_password");
mysql_select_db("$user_database", $connect);
if(!isset($_SESSION['podnetusr'])) {
echo("<html>
<head>
<title>
Pinnacle of Destruction NETWORKS ×× Client Profiles
</title>
</head>
<body bgcolor=black>
<table width=30% align=center><tr><td>");
echo "
<center><img src="http://clan.pinnacleofdestruction.net/login.gif"><p><p></center>
<font size=1 face=verdana color=white><font color=red><b>Note:</b></font> Username and Password are CaSe Sensitive.
Your username and password are the same as your login to the ftp.<p><b>Example 1:</b><br>
<i>Username:
exampleusername@pinnacleofdestruction.net<br>
Password: 123456</i><p>
<b>Example 2:</b><br>
<i>Username:
exampleusername@aulkcrgo.com<br>
Password: 123456</i><br><br>
If you had forgotten your password please retrieve it by going to this page: <a href="http://www.pinnacleofdestruction.net/host/forgotp.php">Forgotten Password Page</a></font>
</left>
<form method="POST" action=$PHP_SELF>
<center>
<table>
<tr>
<td><font color=white size=2>Username:</td>
<td><input type="text" name="username" size="20"></td>
</tr>
<tr>
<td><font color=white size=2>Password:</td>
<td><input type="password" name="password" size="20"></td>
</tr>
<tr>
<td colspan="2">
<p align="center"><input type="submit" value="Submit" name="submit"></td>
</tr>
</table>
</center>
</form>";
exit;
}
$_SESSION["podnetusr"] = $username;
$sql = "SELECT * FROM members WHERE username = "$username" AND password = "$password"";
$result = @mysql_query($sql) or die("No.");
if(mysql_num_rows($result) == "0") {
unset($_SESSION['podnetusr']);
echo("<html>
<head>
<title>
Pinnacle of Destruction NETWORKS ×× Client Profiles
</title>
</head>
<body bgcolor=black>
<table width=30% align=center><tr><td>");
echo "
<center>
<font color=red size=1 face=verdana><b>Username or Password Incorrect!</b></font><br /><br />
<font size=1 face=verdana color=white><font color=red><b>Note:</b></font> Username and Password are CaSe Sensitive.
Your username and password are the same as your login to the ftp.<p><b>Example 1:</b><br>
<i>Username:
exampleusername@pinnacleofdestruction.net<br>
Password: 123456</i><p>
<b>Example 2:</b><br>
<i>Username:
exampleusername@aulkcrgo.com<br>
Password: 123456</i><br><br>
If you had forgotten your password please retrieve it by going to this page: <a href="http://www.pinnacleofdestruction.net/host/forgotp.php">Forgotten Password Page</a></font>
</center>
<form method="POST" action=$PHP_SELF>
<center>
<table>
<tr>
<td><font color=white size=2>Username:</td>
<td><input type="text" name="username" size="20"></td>
</tr>
<tr>
<td><font color=white size=2>Password:</td>
<td><input type="password" name="password" size="20"></td>
</tr>
<tr>
<td colspan="2">
<p align="center"><input type="submit" value="Submit" name="submit"></td>
</tr>
</table>
</center>
</form>";
exit;
}
mysql_close($connect);
?>[/code:1:838babf581]