I found another small bug in catalog article_rss.php ,which prevents the feeds from showing

find (line 39) :

$news_query_raw = tep_db_query("select a.articles_id, a.authors_id, a.articles_date_added, ad.articles_name, ad.articles_head_desc_tag, ad.articles_description, au.authors_name, td.topics_name, a2t.topics_id from " . TABLE_ARTICLES . " a left join " . TABLE_AUTHORS . " au using(authors_id), " . TABLE_ARTICLES_DESCRIPTION . " ad, " . TABLE_ARTICLES_TO_TOPICS . " a2t left join " . TABLE_TOPICS_DESCRIPTION . " td using(topics_id) where (a.articles_date_available IS NULL or to_days(a.articles_date_available)