[Magento 1.6.2.0]Product Flat Data index process issue

We currently have a Magento Community edition 1.6.2.0 store, we're facing issues with "Product Flat Data index process unknown error:exception 'PDOException' with message 'SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`mhtrends_mhtr/#sql-b92_146ef`, CONSTRAINT `FK_CAT_PRD_FLAT_1_ENTT_ID_CAT_PRD_ENTT_ENTT_ID` FOREIGN KEY (`entity_id`) REFERENCES `catalog_product_entity` (`entity_id`) ON DELETE CASCADE ON UPD)' in /home/mhtrends/public_html/lib/Zend/Db/Statement/[login to view URL] This project is a very urgent problem for us, we need to have 100% confirmation project will be able to be completed in the given time frame.