Rsync: failed to set permissions on

Hi ,

I’m using rsync to backup my mybook over the internet to another mybook

I’m having problems with permissions.

The error message is  rsync: failed to set permissions on

The user is a member of a group, that group is the owner of the folders.

When  I tri to chang the owner I get an error " Operation not permitted" the folder is o a external usb disk (/shares/usb1-1share1)

How can I solve this problems