Backup files with Warnings on IIS 6

The backup files are created but four warning messages are displayed and the backup files cannot be listed.

Warning: file_put_contents(backup\backup_migrate\manual/.htaccess): failed to open stream: Permission denied in file_create_htaccess() (line 494 of C:\inetpub\wwwroot\drupal7\includes\file.inc).
Warning: file_get_contents(backup\backup_migrate\manual/test.txt): failed to open stream: Permission denied in backup_migrate_destination_files->check_web_dir() (line 209 of C:\inetpub\wwwroot\drupal7\sites\all\modules\backup_migrate\includes\destinations.file.inc).
Warning: file_put_contents(backup\backup_migrate\manual/.htaccess): failed to open stream: Permission denied in file_create_htaccess() (line 494 of C:\inetpub\wwwroot\drupal7\includes\file.inc).
Warning: file_get_contents(backup\backup_migrate\manual/test.txt): failed to open stream: Permission denied in backup_migrate_destination_files->check_web_dir() (line 209 of C:\inetpub\wwwroot\drupal7\sites\all\modules\backup_migrate\includes\destinations.file.inc).

Default Database backed up successfully to DrupalDev-2014-02-26T08-44-02 in destination Manual Backups Directory in 873.6 ms. (, , delete)