This fixes the way Magento imports data as it just keeps adding ‘straight join’ to the array which uses a lot of memory if your importing a lot of products and will kill the import.

Replace this function in /lib/Varien/Db/Select.php

This has been fixed in the next update and a discussion can be seen here...

http://www.magentocommerce.com/boards/viewthread/113901/

public function __construct(Zend_Db_Adapter_Abstract $adapter)
    {
        parent::__construct($adapter);
        if (!in_array(self::STRAIGHT_JOIN_ON, self::$_joinTypes)) {
            self::$_joinTypes[] = self::STRAIGHT_JOIN_ON;
            self::$_partsInit = array(self::STRAIGHT_JOIN => false) + self::$_partsInit;
        }
    }