If you are using lftp to connect to a secure FTP (SFTP) server using SSL, you may sometimes get the following error during file transfers:
534 Protection level negotiation failed.
In this case, you need to add the following line to the bottom of your /etc/lftp.conf file
set ftp:ssl-protect-data yes
Now try connecting again and hopefully everything should work ok – it sorted my problems when I was trying to connect to the Leeds University SFTP servers using lftp on Ubuntu 9.10 (Karmic).
