I was getting a blank page and and an error using free shipping by categories module.
if you get this error in your web logs...
PHP Fatal error: Call to undefined function tep_get_categories_name() in /patph/to/catalog/includes/modules/shipping/freecats.php on line 74
add to admin/includes/functions/general.php
function tep_get_categories_name($cID, $language = ''){
global $languages_id;
if (!tep_not_null($language))
$language = $languages_id;
$cname = tep_db_fetch_array(tep_db_query('select categories_name from '.TABLE_CATEGORIES_DESCRIPTION.' where categories_id="'.$cID.'" and language_id="'.$language.'"'));
return $cname['categories_name'];
}
I found the fix on an OSC netherlands forum.
http://forums.oscommerce.nl/index.php?showtopic=17881