Can anybody tell me whats wrong with my 12.04/lightdm/XDMCP setup?

i activated X11 remote via tcp and XDMCP on lightdm and restarted lightdm:

[SeatDefaults]
user-session=ubuntu
greeter-session=unity-greeter
xserver-allow-tcp=true

[XDMCPServer]
enabled=true

whenever i try to login to the remove lightdm via Xephyr

Xephyr -query <remote ip> :10

i get the following trace:

SELinux: Disabled on system, not enabling in X server
[dix] Could not init font path element /usr/share/fonts/X11/cyrillic, removing from list!
Ignoring device from udev.
Ignoring device from udev.
Ignoring device from udev.
Ignoring device from udev.
Ignoring device from udev.
Ignoring device from udev.
*** glibc detected *** Xephyr: free(): corrupted unsorted chunks: 0x08659088 ***
======= Backtrace: =========
/lib/i686/cmov/libc.so.6(+0x6af71)[0xb72b6f71]
/lib/i686/cmov/libc.so.6(+0x6c7c8)[0xb72b87c8]
/lib/i686/cmov/libc.so.6(cfree+0x6d)[0xb72bb8ad]
Xephyr(Xfree+0x21)[0x81ddcd1]
Xephyr(SrvXkbResizeKeyType+0x59e)[0x81ca01e]
Xephyr[0x81ab8eb]
Xephyr[0x81ac8c2]
Xephyr[0x8088807]
Xephyr[0x807c16a]
/lib/i686/cmov/libc.so.6(__libc_start_main+0xe6)[0xb7262ca6]
Xephyr[0x8061081]
======= Memory map: ========
08048000-08204000 r-xp 00000000 fd:00 1148994    /usr/bin/Xephyr
08204000-08210000 rw-p 001bc000 fd:00 1148994    /usr/bin/Xephyr
08210000-08239000 rw-p 00000000 00:00 0 
08496000-087ac000 rw-p 00000000 00:00 0          [heap]
b5600000-b5621000 rw-p 00000000 00:00 0 
b5621000-b5700000 ---p 00000000 00:00 0 
b5762000-b588f000 rw-p 00000000 00:00 0 
b588f000-b58b3000 r-xp 00000000 fd:00 50040      /usr/lib/libexpat.so.1.5.2
b58b3000-b58b5000 rw-p 00024000 fd:00 50040      /usr/lib/libexpat.so.1.5.2
b58d0000-b5ae4000 r-xp 00000000 fd:00 1212530    /usr/lib/dri/swrast_dri.so
b5ae4000-b5ae9000 rw-p 00214000 fd:00 1212530    /usr/lib/dri/swrast_dri.so
b5ae9000-b5af8000 rw-p 00000000 00:00 0 
b5af8000-b5c24000 rw-s 00000000 00:04 1420132375  /SYSV00000000 (deleted)
b5c24000-b5c28000 r-xp 00000000 fd:00 770089     /usr/lib/libXfixes.so.3.1.0
b5c28000-b5c29000 rw-p 00003000 fd:00 770089     /usr/lib/libXfixes.so.3.1.0
b5c29000-b5c31000 r-xp 00000000 fd:00 772923     /usr/lib/libXrender.so.1.3.0
b5c31000-b5c32000 rw-p 00007000 fd:00 772923     /usr/lib/libXrender.so.1.3.0
b5c32000-b5c3a000 r-xp 00000000 fd:00 49913      /usr/lib/libXcursor.so.1.0.2
b5c3a000-b5c3b000 rw-p 00007000 fd:00 49913      /usr/lib/libXcursor.so.1.0.2
b5c3b000-b5c58000 r-xp 00000000 09:02 466930     /lib/libgcc_s.so.1
b5c58000-b5c59000 rw-p 0001c000 09:02 466930     /lib/libgcc_s.so.1
b5c59000-b5c5b000 rw-p 00000000 00:00 0 
b5c5b000-b7121000 r-xp 00000000 fd:00 49164      /usr/lib/libnvidia-glcore.so.256.53
b7121000-b7178000 rwxp 014c6000 fd:00 49164      /usr/lib/libnvidia-glcore.so.256.53
b7178000-b7188000 rwxp 00000000 00:00 0 
b7188000-b7189000 r-xp 00000000 fd:00 49193      /usr/lib/tls/libnvidia-tls.so.256.53
b7189000-b718a000 rw-p 00000000 fd:00 49193      /usr/lib/tls/libnvidia-tls.so.256.53
b718a000-b718b000 rw-p 00000000 00:00 0 
b718b000-b7190000 r-xp 00000000 fd:00 50172      /usr/lib/libfontenc.so.1.0.0
b7190000-b7191000 rw-p 00005000 fd:00 50172      /usr/lib/libfontenc.so.1.0.0
b7191000-b71a1000 r-xp 00000000 09:02 466849     /lib/libbz2.so.1.0.4
b71a1000-b71a2000 rw-p 00010000 09:02 466849     /lib/libbz2.so.1.0.4
b71a2000-b71b5000 r-xp 00000000 fd:00 52002      /usr/lib/libz.so.1.2.3.4
b71b5000-b71b6000 rw-p 00013000 fd:00 52002      /usr/lib/libz.so.1.2.3.4
b71b6000-b722a000 r-xp 00000000 fd:00 51162      /usr/lib/libfreetype.so.6.6.0
b722a000-b722e000 rw-p 00073000 fd:00 51162      /usr/lib/libfreetype.so.6.6.0
b722e000-b7246000 r-xp 00000000 fd:00 49652      /usr/lib/libxcb.so.1.1.0
b7246000-b7247000 rw-p 00017000 fd:00 49652      /usr/lib/libxcb.so.1.1.0
b7247000-b7248000 rw-p 00000000 00:00 0 
b7248000-b724b000 r-xp 00000000 fd:00 54148      /usr/lib/libgpg-error.so.0.4.0
b724b000-b724c000 rw-p 00002000 fd:00 54148      /usr/lib/libgpg-error.so.0.4.0
b724c000-b738c000 r-xp 00000000 09:02 467095     /lib/i686/cmov/libc-2.11.3.so