MATE is crashing today on 20.04 after latest update

After the latest "apt upgrade" MATE stopped working for me on Ubuntu 20.04


Gdk-Message: 12:30:52.763: mate-settings-daemon: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.

Gdk-Message: 12:30:52.763: marco: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.

Gdk-Message: 12:30:52.763: mate-panel: Fatal IO error 0 (Success) on X server :0.

Gdk-Message: 12:30:52.763: mate-session: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.

Log isn't very helpful. Ubuntu's Gnome session launched fine so now I'm typing this under Gnome.