Script cambio password...could not query

[dbseo]

<form method='POST'>
    <input type="hidden" name="auser" value="<?php echo $_SESSION['userName']?>" >
    <p><?PHP echo $lang['CURR_PASS']?>:<br />  <input type="password" name="cpass" class="textfield"> </p>
    <p><?PHP echo $lang['NEW_PASS']?>:<br /> <input  type="password" name="npass" class="textfield"></p>
    <p><?PHP echo $lang['CONFIRM_PASS']?>:<br />  <input type="password" name="npassc" class="textfield"></p>
    <input type="submit" name="changepass" class="Button" value="<?PHP echo $lang['UPDATE']?>">
    </form>

if (isset($_POST['changepass']))
{
    $cpass=md5($_POST['cpass']);
    $npass=trim($_POST['npass']);
    $npassc=trim($_POST['npassc']);
    $username=trim(strtolower($_POST['auser']));
    if($npass == $npassc && !empty($npass)){
        $query = "UPDATE members password='".md5(strtolower($npass))."' where username='".$_SESSION['userName']."' and password='$cpass'";
        $result=mysql_query($query) or die("Could not Query"); 

Ho questo codice, per cambiare la password...ma non funziona.
"could not query".
Dove è sbagliato?
Grazie

[Alhazred]

UPDATE members SET password=...

[dbseo]

Grazie mille !