DL2 fails to publish library to FTP site 'at "(null)"'

When I try to publish my Library via FTP using DL2, it fails with a message:

We encountered an error when publishing your library to your FTP site at "(null)".

Operation could not be completed. Login failed.

The file which failed was "//public_html/dlibrary".

If I look at the publishing setup, it never wants to "stick" on the settings I provided for my web host; it keeps defaulting back to the AOL template entry. I've tried deleting and recreating the settings; no good. I even tried deleting the keychain entry that DL2 created, and then recreating the account in DL2; no change.

It did work once, when DL2 first came out...

I can reach the site manually, and with other FTP clients, using the same parameters.

This feature is a big part of why I paid for the DL2 upgrade. Reading the support forums, it seems like publish-to-web is very broken. I'm very disappointed; DL2 isn't working as advertised. When will the various issues with FTP publication be fixed? In particular, I'd really prefer to use SFTP, to protect my account login...