Identified the possible reasons for failure along with the network configuration on the source (host.allow/hosts.deny):
Host SSH server is not using RSA protocol 2 keys. If it uses only DSA or RSA1 keys, then Converter cannot connect to the source (it is a bug in the product introduced in version 5.1). You can check this configuration in your sshd config file (by default under /etc/ssh/sshd_config).
I don't have a clue how the hardware version on the destination can affect this behavior.