Puoi provare con questo suggerimento (trovato sul manuale ufficiale usando il tuo errore come chiave di ricerca su google):

If when using ftp_put you get the one of the following errors:

Warning: ftp_put() [function.ftp-put]: Opening ASCII mode data connection

Warning: ftp_put() [function.ftp-put]: Opening BINARY mode data connection

and it creates the file in the correct location but is a 0kb file and all FTP commands thereafter fail. It is likely that the client is behind a firewall. To rectify this use:

<?php
ftp_pasv($resource, true);
?>

Before executing any put commands. Took me so long to figure this out I actually cheered when I did
http://www.php.net/manual/en/function.ftp-put.php#90518