If your error says:
FTP error: Server was unable to complete action (Example: 'Directory change failed' or 'Access denied')
FTP proc: ftp_upload_core_cwd_type_stox::sendCWD
The ftp directory name must be the absolute directory where your images are stored. For example, some servers require that you insert /home/XXX/public_html (or something similar) before the directory name for the images.