As for FileZilla you should refer your question to their support. Some time before I've asked the same on FileZilla's forums, and they do not seem to be going to provide a fix for it.
For now if you don't use RSA keys for sFTP (if you run sFTP support with a help of ProFTPd), you should disable publickey from auth method in /etc/proftpd.sftp.conf and take care to copy it under custombuild/custom/proftpd/conf/ folder.