The module is no longer able to backup and save the file after upgrading to ver. 7.2 . I've triple checked the permission and the .htacess file, everything seems to be fine.

Here is the error msg,

    Security notice: Backup and Migrate will not save backup files to the server because the destination directory is publicly accessible. If you want to save files to the server, please secure the 'sites/default/files/private/backup_migrate/manual' directory
    Security notice: Backup and Migrate will not save backup files to the server because the destination directory is publicly accessible. If you want to save files to the server, please secure the 'sites/default/files/private/backup_migrate/manual' directory
    Could not run backup because the file could not be saved to the destination.

I am using Nginx as the frontend server which passes the requests to Apache listening to port 8080. I can still conduct backup and save the file to exact the same directory without any problem by adding :8080 to the url.