Remove Comma after products_options_values_name . your query should as below
$products_options_query = tep_db_query("select pov.products_options_values_id, pov.products_options_values_name, pa.options_values_price, pa.price_prefix from " . TABLE_PRODUCTS_ATTRIBUTES . " pa, " . TABLE_PRODUCTS_OPTIONS_VALUES . " pov where pa.products_id = '" . (int)$HTTP_GET_VARS['products_id'] . "' and pa.options_id = '" . (int)$products_options_name['products_options_id'] . "' and pa.options_values_id = pov.products_options_values_id and pov.language_id = '" . (int)$languages_id . "' group by pov.products_options_values_name order by pov.products_options_values_id desc");