Comment 3 for bug 1067797

It segfaults somewhere in gobject introspection code. On Ubuntu this is the package python3-gi. It would perhaps help to install debug symbols and re-run it in gdb to get symbols for the topmost two entries of the stack. On Ubuntu the symbols are inpython3-gi-dbg. I guess the Arch package is python-gobject-dbg or something.

I've removed the unrelated packages from you list, that leaves these:
[2012-10-17 14:40] upgraded python-dbus-common (1.1.1-1 -> 1.1.1-2)
[2012-10-17 14:40] upgraded ibus (1.4.2-1 -> 1.4.2-2)
[2012-10-17 14:40] upgraded python (3.2.3-3 -> 3.3.0-1)
[2012-10-17 14:40] upgraded python-cairo (1.10.0-1 -> 1.10.0-2)
[2012-10-17 14:40] upgraded python-dbus (1.1.1-1 -> 1.1.1-2)
[2012-10-17 14:40] upgraded python-distutils-extra (2.32-1 -> 2.37-1)
[2012-10-17 14:40] upgraded python-gobject (3.2.2-1 -> 3.2.2-2)
[2012-10-17 14:40] upgraded python-virtkey (0.61.0-1 -> 0.61.0-2)

The big thing that sticks out is python itself, apparently Arch just upgraded to python 3.3. That's a first for Onboard, I haven't tried it yet. Will do here and let you know. The second is perhaps python-gobject, it's 3.2.2 there, while Ubuntu's python-gi is at 3.4.0.