plugin localizzated: it doesn't translate it

[surferbloggy]

Hi i've done a wordpress plugin, i've done th the localization as explained here so i've generated the po and mo file for the new languages and i've done the traslations
the words to traslate are this way

<?php _e('System Settings', 'wp-myplugin-name'); ?>
or _e('System Settings', 'wp-myplugin-name')

but in the italian wordpress version it isn't traslated
is the position of the wordpress code wrong??

i've added this function

public function wp__i18n_init() {
        $pluginDir = dirname(plugin_basename(__FILE__));
        load_plugin_textdomain('wp-myplugin-name', false, $pluginDir . '/languages/');
    }

and this line

add_action( 'plugins_loaded', array(&$this, 'wp__i18n_init') );

in the public function addActionsAndFilters()

could you help me to understand why doesn't traslate it??
thank you for your help