$ linuxcnc rdelta.ini 
LINUXCNC - 2.6.0~pre joints_axes
Machine configuration directory is '/home/chris/emc2.trunk/configs/sim/axis'
Machine configuration file is 'rdelta.ini'
Starting LinuxCNC...
io started
halcmd loadusr io started
task pid=20854
emcTaskInit: using builtin interpreter
/home/chris/emc2.trunk/scripts/linuxcnc: line 716: 20855 Segmentation fault      (core dumped) $EMCDISPLAY -ini "$INIFILE" $EMCDISPLAYARGS $EXTRA_ARGS
Shutting down and cleaning up LinuxCNC...
Cleanup done
LinuxCNC terminated with an error.  You can find more information in the log:
    /home/chris/linuxcnc_debug.txt
and
    /home/chris/linuxcnc_print.txt
as well as in the output of the shell command 'dmesg' and in the terminal
chris@magneto:~/emc2.trunk/configs/sim/axis$ gdb /usr/bin/python core
GNU gdb (Ubuntu/Linaro 7.4-2012.04-0ubuntu2.1) 7.4-2012.04
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.launchpad.net/gdb-linaro/>...
Reading symbols from /usr/bin/python...(no debugging symbols found)...done.

warning: core file may not match specified executable file.
[New LWP 20855]
[New LWP 20859]
[New LWP 20856]

warning: Can't read pathname for load map: Input/output error.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `/usr/bin/python /home/chris/emc2.trunk/bin/axis -ini /home/chris/emc2.trunk/con'.
Program terminated with signal 11, Segmentation fault.
#0  _XData32 (dpy=0x23b5f00, data=<optimized out>, len=600) at ../../src/XlibInt.c:1759
1759	../../src/XlibInt.c: No such file or directory.
(gdb) bt
#0  _XData32 (dpy=0x23b5f00, data=<optimized out>, len=600) at ../../src/XlibInt.c:1759
#1  0x00007ff535067252 in XChangeProperty (dpy=0x23b5f00, w=<optimized out>, property=305, type=<optimized out>, format=32, mode=0, data=0x309ca44 "\020", nelements=8336) at ../../src/ChProp.c:83
#2  0x00007ff5285126a9 in seticon (s=<optimized out>, o=<optimized out>) at emc/usr_intf/axis/extensions/seticon.c:173
#3  0x0000000000466254 in PyEval_EvalFrameEx ()
#4  0x000000000057bd02 in PyEval_EvalCodeEx ()
#5  0x000000000057c77d in PyRun_FileExFlags ()
#6  0x000000000057e4a1 in PyRun_SimpleFileExFlags ()
#7  0x0000000000512cfd in Py_Main ()
#8  0x00007ff536e8776d in __libc_start_main () from /lib/x86_64-linux-gnu/libc.so.6
#9  0x000000000041ba51 in _start ()
(gdb)