Error during product modify

[Ballastico]

Hi everyone.
I have a site with VM 2.6.0 that always worked.
Last time when I go to change a product price and save I have the following error in the upper part of the screen:

        vmError: VmTableData::store failed - Duplicate entry '0' for key 'PRIMARY' SQL=INSERT INTO `intv2_virtuemart_products_it_it` (`virtuemart_product_id`,`product_name`,`product_s_desc`,`product_desc`,`metadesc`,`metakey`,`customtitle`,`slug`) VALUES ('0','prova','','','','','','prova')
        vmError: Product store TableProducts: :store fallito - Unknown column 'product_gtin' in 'field list' SQL=INSERT INTO `intv2_virtuemart_products` (`virtuemart_product_id`,`virtuemart_vendor_id`,`product_parent_id`,`product_sku`,`product_gtin`,`product_mpn`,`product_weight_uom`,`product_lwh_uom`,`product_url`,`product_in_stock`,`product_ordered`,`low_stock_notification`,`product_available_date`,`product_availability`,`product_special`,`product_sales`,`product_unit`,`product_params`,`intnotes`,`metarobot`,`metaauthor`,`layout`,`published`,`created_on`,`created_by`,`modified_on`,`modified_by`) VALUES ('0','1','0','prova','','','KG','M','','0','0','0','2014-11-18','','0','0','KG','min_order_level=\"\"|max_order_level=\"\"|step_order_level=\"\"|product_box=\"\"|','','','','0','1','2014-11-18 18:11:41','386','2014-11-18 18:11:41','386')
        vmError: You are not an administrator or the correct vendor, storing of product cancelled

Ca someone help me?
Thanks a lot.

[Ballastico]

Please someone?