If you're getting "There was a problem with reindexing process." error and "Integrity constraint violation: 1452 Cannot add or update a child row" in your exception.log, it can be caused by missing table prefixes in Magento sample data dump.
Fortunately, there's a way to fix it.
The actual error in the exeption log that can point to missing prefixes can look somewhat like this for Magento 1.6:
SQLSTATE: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`magento`.`mage1610_cataloginventory_stock_status`, CONSTRAINT `FK_CATINV_STOCK_STS_PRD_ID_CAT_PRD_ENTT_ENTT_ID` FOREIGN KEY (`product_id`) REFERENCES `catalog_product_entity` (`entity_id`) ON)
If you check the error carefully, you'll notice that `catalog_product_entity` table is wrong and should be actually called `mage1610_catalog_product_entity`.
If you are using prefixes in your Magento installation, you should dump your database and check every corresponding operation for table prefixes. If it is indeed your issue, you should be able to fix it by adding all missing prefixes and importing your dump back in the database.
You might also want to use our Magento Sample Data Prefix Script to adapt Magento Sample Data for a prefixed Magento installation.