onUserAfterSave ne marche pas

[Visiteur]

Bonjour

j'essaye de cree un plugin tres simple sur l'event onUserAfterSave il est active et j'utilise J173

un exemple de test

onUserAfterSave.php

<?php
defined('_JEXEC') or die('Restricted access');
jimport('joomla.plugin.plugin');
class plgUserAfterSave extends JPlugin
{
	function onUserAfterSave ($user, $isnew, $success, $msg)
	{
		$tablename = $params->get('tablename');
		$db = JFactory::getDbo();
		$query = "INSERT INTO #__".$tablename." (user_id,first_name,last_name) VALUES (100,'AA','BB');";
		$db->setQuery($query);
                $db->query ();
	}
}
?>

onUserAfterSave.xml

<?xml version="1.0" encoding="utf-8"?>

<install version="1.7" type="plugin" group="user" method="upgrade">
	<name>onUserAfterSave</name>
	<author>onUserAfterSave</author>
	<creationDate>January 2012</creationDate>
	<copyright>Copyright 2008 - 2010 by Slashes &amp; Dots Sdn Bhd. All rights reserved</copyright>
	<license>http://www.gnu.org/licenses/gpl-2.0.html GNU/GPL</license>
	<authorEmail>support@jomsocial.com</authorEmail>
	<authorUrl>http://www.jomsocial.com</authorUrl>
	<version>1.0.0</version>
	<description>onUserAfterSave</description>
	<files>
		<filename plugin="onUserAfterSave">onUserAfterSave.php</filename>
	</files>
	<config>
		<fields name="params">
			<fieldset name="basic">
		<field name="tablename"
		       type="text" size="40"				
			description="Nom de la table"
			label="Nom de la table"
			default="userstest"
		/>
			</fieldset>
		</fields>
	</config>
</install>

absolument rien ne se passe

bien sur la table existe et si je fait l'insertion dans phpmyadmin ca marche

on dirait que onUserAfterSave n'est pas appelé

merci pour l'aide