Some days ago I updated my arch. Since this time I could not start xfce any more. It says "unsupported high keycode 372 for name <I372> ignored X11 cannot support keycodes above 255. This warning only shows for the first high keycode. If I start openbox with the xfce-panel I can start, but after exit I get the same message.
Which version of xorg-xkbcomp are you using? A possibly related commit was introduced in xkbcomp 1.4.2. See https://cgit.freedesktop.org/xorg/app/xkbcomp/commit/?id=5bc2849273a224a2df593b7e8df31f0bde666482