Here, doing "ip addr" or "ifconfig" indeed reported that lo has no IP, so I inspected /etc/network/interfaces and, sure enough, there was no stanza for the lo interface. Having fixed this and rebooted, everything seems back to normal. Kiitoksia, Pekka!
Note that, for some odd reason, X11 forwarding seems to be disabled in /etc/ssh/ssh_config by default, on recent installs. Once that was enabled too, life returned to normal. Hurray!
I concur with Pekka.
Here, doing "ip addr" or "ifconfig" indeed reported that lo has no IP, so I inspected /etc/network/ interfaces and, sure enough, there was no stanza for the lo interface. Having fixed this and rebooted, everything seems back to normal. Kiitoksia, Pekka!
Note that, for some odd reason, X11 forwarding seems to be disabled in /etc/ssh/ssh_config by default, on recent installs. Once that was enabled too, life returned to normal. Hurray!