When backing up files beginning with a period from a Windows system to a remote FTP server running Linux, the directory containing these files can not be removed by Cobian Backup due to the fact that it cannot delete these files that begin with a period. (The folder deletion is triggered by CB to limit the number of copies to keep of the backup.)
However, Windows Explorer or any other FTP client are able to delete these files without any problem. The files are created under Windows and have read/write attributes on the FTP server.