This only happens for category and search pages and the reason is that functions/bfa_meta_tags.php line 75 and 83 (Atahualpa 3.4.1) doesn't have a charset in htmlentities, which makes it revert back to iso-8859-1 instead of utf-8.
I changed the hardcoded lines to this to solve the problem temporary:
$bfa_ata_page_title = htmlentities(single_cat_title('', false),ENT_QUOTES,"UTF-8");
$bfa_ata_page_title = htmlentities(wp_specialchars($s),ENT_QUOTES,"UTF-8 );
Hope this change makes it to a later release.