As Noted in Start Part 3 - Delete Images, Import... you have an older AdminImport.php file with a bug that needs to be fixed. You can get the file from:
http://www.prestashop.com/forums/
Or Click the AdminImport.zip file attached below!
FTP the new AdminImport.php file into /admin/tabs directory of your PrestaShop.
Important Note: See this FAQ about always using the AdminImport.php file below!