[sork] failure in changing password for horde authentication:user not found

[Nada Aziz]

Dear all;
i know i allready post this but i have not found a solution yet therefore i am posting it again.
i configured the password module with my already existing horde web mail  but when i try to change the password it says ( failure in changing password for horde authentication:user not found) i am using mysql driver.
here is my conf.php:
<?php
/* CONFIG START. DO NOT CHANGE ANYTHING IN OR AFTER THIS LINE. */
// $Horde: passwd/config/conf.xml,v 1.12.2.1 2008/10/09 17:12:03 jan Exp $
$conf['menu']['apps'] = array();
$conf['backend']['backend_list'] = 'hidden';
$conf['user']['change'] = true;
$conf['user']['refused'] = array('root', 'bin', 'daemon', 'adm', 'lp', 'shutdown', 'halt', 'uucp', 'ftp', 'anonymous', 'nobody', 'httpd', 'operator', 'guest', 'diginext', 'bind', 'cyrus', 'courier', 'games', 'kmem', 'mailnull', 'man', 'mysql', 'news', 'postfix', 'sshd', 'tty', 'www');
$conf['password']['strengthtests'] = false;
$conf['hooks']['full_name'] = true;
$conf['hooks']['default_username'] = false;
$conf['hooks']['username'] = false;
$conf['hooks']['userdn'] = false;
/* CONFIG END. DO NOT CHANGE ANYTHING IN OR BEFORE THIS LINE. */

and here is my backends.php:

 
$backends['hordesql'] = array (
    'name' => 'Horde Authentication',
    'preferred' => '',
    'password policy' => array(
        'minLength' => 3,
        'maxLength' => 8,
        'maxSpace' => 0,
        'minUpper' => 0,
        'minLower' => 0,
        'minNumeric' => 0,
        'minSymbol' => 0
    ),
    'driver' => 'sql',
    'params' => array_merge($conf['sql'],
                            array('table' => 'horde_users',
                                  'user_col' => 'user_uid',
                                  'pass_col' => 'user_pass',
                                  'show_encryption' => false)),
);
 



i also cross checked the mysql horde database and the table's name is "horde_users" and the user column is "user_uid" and the password column is "user_pass".
any help will be appreciated, thanks in advance.