This problem was partially fixed by clearing my .x2go and .x2goclient dirs, meaning it might be a combination of ecdsa keys in .ssh and something in .x2go*.

There is still the problem where x2goclient asks for a passphrase and you have to click cancel (pressing escape will result in an "authentication failed" dialog).

Anders Bruun Olsen
Det Danske Sprog- og Litteraturselskab
(Society for Danish Language and Literature)