Use powweb_php.ini for powweb.com hosting.

create a folder in the root of your hosting called tmp with chmod 777

Rename powweb_php.ini to php.ini

Open your newly renamed php.ini file and change the path for session.save_path = to the path of the tmp folder you created. For example: "/www/z/URL_NAME_HERE/htdocs/tmp"

You can find the path in your server_info.php file at http://www.YOUR_SITE_HERE.com/manager/server_info.php

Upload the php.ini file to the root of your PhotoStore site and also upload a copy to the manager directory.

If that doesn't work upload a copy to the root of your hosting account.