After upgrading to x2goserver 4.0.1.8 the keyboard is completely screwed up
in x2goclient on Mac.
Downgrading x2goserver to 4.0.1.6 fixes the problem. The problem must have
been introduced in 4.0.1.7 or 4.0.1.8. Perhaps that new keyboard layout
detection?
My setup:
Server is Ubuntu 12.04 with XFCE 4.10.
Client is OSX 10.9 and I have tested with x2goclient 4.0.0.4, 4.0.1.1 and
latest git.

can you be available on IRC tomorrow for tracking this down? There actually is a commit that probably has caused this, so you should already manually revert that commit [1] on your servers.