I have bazaar version 728 of Ubercart installed. Flatrate quotes work for me in this version. Since the database table has changed you need to run update.php. I would suggest disabling then uninstalling flatrate before installing the new version. Then enable the new version and run update.php. You will have to configure the flatrate module at admin/store/settings/quotes/methods/flatrate before you can turn it on in the menu at admin/store/settings/quotes/methods