I did a bit of testing today, and managed to set it running. I happen to have a non-standard port declared as default for ssh connections in my .ssh/config file, in the form:
at the end of the file, because I have the custom of setting my installed servers apart from the default 22, to minimize attacks from port scanners. And not all my remote machines are declared in the config file, so this line takes care of the forgotten ones. If I comment out that line, x2goclient works again, both connecting to the default port 22 or to a non-standard port.
It didn't matter before if I was connecting to a standard setup in port 22, or a custom one. It always choked at that line.
This line doesn't give problems in my ssh connections, though. Perhaps there is a problem somewhere in the parsing of the ssh config file? Where should I report that?
Thanks for taking your time in answering (and motivating me in digging more on this... ;-) ). It was really a nuisance, i use x2go in a lot if machines.