I found in error_logs. I don't understand where is the issue, is trying to insert two times in table ps_specific_price?:
Exception
Message:
ThirtyBeesDatabaseException: Duplicate key value
ThirtyBeesDatabaseException: Duplicate entry '1547-0-0-0-2014-08-01 00:13:44-2014-08-31 23:59:00-1-0-0-0-0-1-1' for key 'id_product_2'
Location:
classes/ObjectModel.php line 640
SQL
INSERT INTO `ps_specific_price` (`id_specific_price_rule`, `id_cart`, `id_product`, `id_shop`, `id_shop_group`, `id_currency`, `id_country`, `id_group`, `id_customer`, `id_product_attribute`, `price`, `from_quantity`, `reduction`, `reduction_tax`, `reduction_type`, `from`, `to`) VALUES ('1', '0', '1547', '1', '0', '0', '0', '0', '0', '0', '-1', '1', '0.08', '1', 'percentage', '2014-08-01 00:13:44', '2014-08-31 23:59:00')