FreeBSD 10.0-CURRENT/amd r234000: Xorg/xdm startup failure when started via /etc/ttys

Since I recompiled this morning the sources of FreeBSD
10.0-CURRENT/amd64 (r234000), I have a very strange behaviour of xdm
started via /etc/ttys.
For a short moment the xdm login requester is shown on the screen and
then the console is visible again.
Well, I tried to investigate the problem and thought it might could me a
corrupt installation, but this error occured out of the sudden after a
make world this morning.

When trying starting xdm from the console (not the /etc/tty entry), I
get a login requester and X11 as usual.

/var/log/xdm.log contains:

Build Date: 07 April 2012  04:51:08PM

Current version of pixman: 0.24.2
        Before reporting problems, check http://wiki.x.org
        to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
        (++) from command line, (!!) notice, (II) informational,
        (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.0.log", Time: Sat Apr  7 18:38:24 2012
(==) Using config file: "/etc/X11/xorg.conf"
xdm info (pid 2055): sourcing /usr/local/share/X11/xdm/Xsetup_0
xdm error (pid 2050): Unknown session exit code 2560 from process 2055
xdm info (pid 2050): Exiting


The file  /usr/local/share/X11/xdm/Xsetup_0 contains xsetroot command
setting background to black, but even commenting out everything let xdm
fail.

In /var/log/Xorg.0.log, I find nothing unusual.


I saw changes to "init.c" this morning ...?

I'm a little bit helpless ...

Regards,
Oliver