Backup to FTP folder seems to create multiple folders with same name "automatically"

[peacock]

I have an odd problem when doing a large (26 GByte) domain and data (without mail) backup. I created at the top level of my folder/file structure when viewed via the Plesk 11 GUI under a folder called /private/backup I know can be written into. But when I go to FTP repository settings (after creating an FTP user with the same /private/backup directory as destination) and then to Backup Manager and launch a backup, I see the result not in my FTP repository, but rather as a server backup. And at the same time I get a failure message in the backup status tab. Then when I go to file manager I see lo and behold not under /private/backup but rather under /private/backup/private/backup !!! the 26GByte tar file ready to be downloaded, at which point I must go into my FTP user and change the directory structure to /private/backup/private/backup and I can then download the file. Can someone tell me what's going on with this duplicate structure that automatically happens. No, I wasn't drunk and seeing double when I set up /private/backup as the original backup file destination. Also I have many large tar files in my .../PMM/tmp directory. Can I kill the tar files there? Can I kill everything there?
Since I see a list of failed messages via the GUI of Plesk under the Backup Status tab I can't remove by clicking the Remove link there I assume these are messages are linked to the junk still in .../PMM/tmp