/**
* Multilingual settings
*
* This is a collection of variables that can be set up for each language when i18n is enabled.
* These are the basic ones for Drupal core, but you can add your own here.
*/
$conf['i18n_variables'] = array(
// Site name, slogan, mission, etc..
'site_name',
'site_slogan',
'site_mission',
'site_footer',
'anonymous',
// Different front page for each language
'site_frontpage',
// Primary and secondary links
'menu_primary_links_source',
'menu_secondary_links_source',
// Contact form information
'contact_form_information',
);

http://openflows.com/blog/mvc/2008/10/03/drupal-6-i18n-basics

Put this in settings.php

Drupal 6: Translatable primary and secondary links with i18n module

module, drupal

PHP