Same here:
Fatal error: Uncaught exception 'Exception' with message 'Argument 1 for HMBKP_Scheduled_Backup::set_reoccurrence must be a valid cron reoccurrence or "manually"' in /home/mysite/public_html/wp-content/plugins/backupwordpress/classes/schedule.php:484 Stack trace: #0 /home/mysite/public_html/wp-content/plugins/backupwordpress/functions/core.php(151): HMBKP_Scheduled_Backup->set_reoccurrence('hmbkp_weekly') #1 /home/mysite/public_html/wp-content/plugins/backupwordpress/backupwordpress.php(156): hmbkp_update() #2 [internal function]: hmbkp_init('') #3 /home/mysite/public_html/wp-includes/plugin.php(406): call_user_func_array('hmbkp_init', Array) #4 /home/mysite/public_html/wp-admin/admin.php(111): do_action('admin_init') #5 /home/mysite/public_html/wp-admin/plugins.php(10): require_once('/home/mysite/...') #6 {main} thrown in /home/mysite/public_html/wp-content/plugins/backupwordpress/classes/schedule.php on line 484
Doesn’t help to uninstall/re-install, either. Even cleaned the database.