I first noticed this problem a few days ago after attempting to update to 1.7.4 (i think). The plugin activates fine but when I try to go to its settings page under Tools I get a blank screen. In the server error log, I see the following:
PHP Fatal error: Call to undefined method WP_List_Table::WP_List_Table() in /srv/www/x.com/public_html/wp-content/plugins/backwpup/app/list-tables.php on line 8, referer: http://x.com/wp-admin/plugins.php?activate=true&plugin_status=all&paged=1&s=
Note: I replaced the url with x.com.