Better traceback from gdb with python-dbg installed:

This happens even if no GUI is instantiated, so webkit may not be guilty.

#0  0x00007ffff6a8e1a8 in poll () from /lib/libc.so.6
#1  0x00007ffff5868979 in ?? () from /lib/libglib-2.0.so.0
#2  0x00007ffff5869125 in g_main_loop_run () from /lib/libglib-2.0.so.0
#3  0x00007ffff4818a47 in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#4  0x00007ffff4ed2852 in ?? () from /usr/lib/pymodules/python2.6/gtk-2.0/gtk/_gtk.so
#5  0x00000000004a52e8 in call_function (f=
    Frame 0x1635b00, for file /usr/lib/python2.6/dist-packages/twisted/internet/gtk2reactor.py, line 270, in run (self=<Gtk2Reactor(waker=<_UnixWaker(i=9, fileno=<function at remote 0x12c8de8>, reactor=<...>, o=10) at remote 0x15e1d10>, threadCallQueue=[], _cancellations=0, _sources={<...>: 5}, _justStopped=False, _newTimedCalls=[], _pendingTimedCalls=[], _Gtk2Reactor__iteration=<built-in function main_iteration>, _internalReaders=set([<...>]), _started=True, _simtag=260, _Gtk2Reactor__run=<built-in function main>, usingThreads=True, _eventTriggers={'startup': <_ThreePhaseEvent(during=[], state='BASE', after=[], finishedBefore=[], before=[]) at remote 0x15e1c50>, 'shutdown': <_ThreePhaseEvent(during=[(<instancemethod at remote 0x1008e60>, (), {}), (<instancemethod at remote 0x1008eb0>, (...), {})], state='BASE', after=[], before=[]) at remote 0x15e1c90>}, _installSignalHandlers=1, _Gtk2Reactor__pending=<built-in function events_pending>, running=True, resolver=<ThreadedResolver(_runningQueries={}, reactor=<...>) ...(truncated), throwflag=<value optimized out>)
    at ../Python/ceval.c:3734
#6  PyEval_EvalFrameEx (f=
    Frame 0x1635b00, for file /usr/lib/python2.6/dist-packages/twisted/internet/gtk2reactor.py, line 270, in run (self=<Gtk2Reactor(waker=<_UnixWaker(i=9, fileno=<function at remote 0x12c8de8>, reactor=<...>, o=10) at remote 0x15e1d10>, threadCallQueue=[], _cancellations=0, _sources={<...>: 5}, _justStopped=False, _newTimedCalls=[], _pendingTimedCalls=[], _Gtk2Reactor__iteration=<built-in function main_iteration>, _internalReaders=set([<...>]), _started=True, _simtag=260, _Gtk2Reactor__run=<built-in function main>, usingThreads=True, _eventTriggers={'startup': <_ThreePhaseEvent(during=[], state='BASE', after=[], finishedBefore=[], before=[]) at remote 0x15e1c50>, 'shutdown': <_ThreePhaseEvent(during=[(<instancemethod at remote 0x1008e60>, (), {}), (<instancemethod at remote 0x1008eb0>, (...), {})], state='BASE', after=[], before=[]) at remote 0x15e1c90>}, _installSignalHandlers=1, _Gtk2Reactor__pending=<built-in function events_pending>, running=True, resolver=<ThreadedResolver(_runningQueries={}, reactor=<...>) ...(truncated), throwflag=<value optimized out>)
    at ../Python/ceval.c:2412
#7  0x00000000004a6bd1 in PyEval_EvalCodeEx (co=0x12c86c0, globals=<value optimized out>, locals=<value optimized out>, args=0x2, 
    argcount=<value optimized out>, kws=<value optimized out>, kwcount=0, defs=0x13c8d28, defcount=1, closure=0x0) at ../Python/ceval.c:3000
#8  0x00000000004a4d59 in fast_function (f=
    Frame 0x1633560, for file /usr/lib/ubuntu-sso-client/ubuntu-sso-login, line 221, in main (self=<LoginMain(_LoginMain__bus=<SessionBus(_bus_type=0, _signals_lock=<thread.lock at remote 0x7fffeefaacd8>, _Connection__call_on_disconnection=[], _dbus_Connection_initialized=1, _bus_names=<WeakValueDictionary(_remove=<function at remote 0x7fffecbcb488>, data={'com.ubuntu.sso': <KeyedRef at remote 0x1260e90>}) at remote 0xcc3e18>, _signal_sender_matches={}, _signal_recipients_by_object_path={None: {'com.ubuntu.sso': {'AuthorizationDenied': [<SignalMatch at remote 0x15e5050>], 'NewCredentials': [<SignalMatch at remote 0x148af50>], 'OAuthError': [<SignalMatch at remote 0x15e5110>]}}}) at remote 0x12427d0>) at remote 0x15e1f10>, reactor=<Gtk2Reactor(waker=<_UnixWaker(i=9, fileno=<function at remote 0x12c8de8>, reactor=<...>, o=10) at remote 0x15e1d10>, threadCallQueue=[], _cancellations=0, _sources={<...>: 5}, _justStopped=False, _newTimedCalls=[], _pendingTimedCalls=[], _Gtk2Reactor__iteration=<built-in function main_i...(truncated), throwflag=<value optimized out>)
    at ../Python/ceval.c:3846
#9  call_function (f=
    Frame 0x1633560, for file /usr/lib/ubuntu-sso-client/ubuntu-sso-login, line 221, in main (self=<LoginMain(_LoginMain__bus=<SessionBus(_bus_type=0, _signals_lock=<thread.lock at remote 0x7fffeefaacd8>, _Connection__call_on_disconnection=[], _dbus_Connection_initialized=1, _bus_names=<WeakValueDictionary(_remove=<function at remote 0x7fffecbcb488>, data={'com.ubuntu.sso': <KeyedRef at remote 0x1260e90>}) at remote 0xcc3e18>, _signal_sender_matches={}, _signal_recip---Type <return> to continue, or q <return> to quit---
ients_by_object_path={None: {'com.ubuntu.sso': {'AuthorizationDenied': [<SignalMatch at remote 0x15e5050>], 'NewCredentials': [<SignalMatch at remote 0x148af50>], 'OAuthError': [<SignalMatch at remote 0x15e5110>]}}}) at remote 0x12427d0>) at remote 0x15e1f10>, reactor=<Gtk2Reactor(waker=<_UnixWaker(i=9, fileno=<function at remote 0x12c8de8>, reactor=<...>, o=10) at remote 0x15e1d10>, threadCallQueue=[], _cancellations=0, _sources={<...>: 5}, _justStopped=False, _newTimedCalls=[], _pendingTimedCalls=[], _Gtk2Reactor__iteration=<built-in function main_i...(truncated), throwflag=<value optimized out>)
    at ../Python/ceval.c:3771
#10 PyEval_EvalFrameEx (f=
    Frame 0x1633560, for file /usr/lib/ubuntu-sso-client/ubuntu-sso-login, line 221, in main (self=<LoginMain(_LoginMain__bus=<SessionBus(_bus_type=0, _signals_lock=<thread.lock at remote 0x7fffeefaacd8>, _Connection__call_on_disconnection=[], _dbus_Connection_initialized=1, _bus_names=<WeakValueDictionary(_remove=<function at remote 0x7fffecbcb488>, data={'com.ubuntu.sso': <KeyedRef at remote 0x1260e90>}) at remote 0xcc3e18>, _signal_sender_matches={}, _signal_recipients_by_object_path={None: {'com.ubuntu.sso': {'AuthorizationDenied': [<SignalMatch at remote 0x15e5050>], 'NewCredentials': [<SignalMatch at remote 0x148af50>], 'OAuthError': [<SignalMatch at remote 0x15e5110>]}}}) at remote 0x12427d0>) at remote 0x15e1f10>, reactor=<Gtk2Reactor(waker=<_UnixWaker(i=9, fileno=<function at remote 0x12c8de8>, reactor=<...>, o=10) at remote 0x15e1d10>, threadCallQueue=[], _cancellations=0, _sources={<...>: 5}, _justStopped=False, _newTimedCalls=[], _pendingTimedCalls=[], _Gtk2Reactor__iteration=<built-in function main_i...(truncated), throwflag=<value optimized out>)
    at ../Python/ceval.c:2412
#11 0x00000000004a5ab0 in fast_function (f=Frame 0x939670, for file /usr/lib/ubuntu-sso-client/ubuntu-sso-login, line 248, in <module> (), 
    throwflag=<value optimized out>) at ../Python/ceval.c:3836
#12 call_function (f=Frame 0x939670, for file /usr/lib/ubuntu-sso-client/ubuntu-sso-login, line 248, in <module> (), throwflag=<value optimized out>)
    at ../Python/ceval.c:3771
#13 PyEval_EvalFrameEx (f=Frame 0x939670, for file /usr/lib/ubuntu-sso-client/ubuntu-sso-login, line 248, in <module> (), throwflag=<value optimized out>)
    at ../Python/ceval.c:2412
#14 0x00000000004a6bd1 in PyEval_EvalCodeEx (co=0x7ffff7f07828, globals=<value optimized out>, locals=<value optimized out>, args=0x0, 
    argcount=<value optimized out>, kws=<value optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0) at ../Python/ceval.c:3000
#15 0x00000000004a6ca2 in PyEval_EvalCode (co=0x15dbae0, globals=<unknown at remote 0x6>, locals=<unknown at remote 0x45>) at ../Python/ceval.c:541
#16 0x00000000004c701e in run_mod (fp=<value optimized out>, filename=0x7fffffffe517 "/usr/lib/ubuntu-sso-client/ubuntu-sso-login", 
    start=<value optimized out>, globals=<value optimized out>, locals=<value optimized out>, closeit=1, flags=0x7fffffffe0f0) at ../Python/pythonrun.c:1351
#17 PyRun_FileExFlags (fp=<value optimized out>, filename=0x7fffffffe517 "/usr/lib/ubuntu-sso-client/ubuntu-sso-login", start=<value optimized out>, 
    globals=<value optimized out>, locals=<value optimized out>, closeit=1, flags=0x7fffffffe0f0) at ../Python/pythonrun.c:1337
#18 0x00000000004c7234 in PyRun_SimpleFileExFlags (fp=<value optimized out>, filename=0x7fffffffe517 "/usr/lib/ubuntu-sso-client/ubuntu-sso-login", 
    closeit=1, flags=0x7fffffffe0f0) at ../Python/pythonrun.c:941
#19 0x00000000004180c1 in Py_Main (argc=-135348096, argv=<value optimized out>) at ../Modules/main.c:577
#20 0x00007ffff69d2d8e in __libc_start_main () from /lib/libc.so.6
#21 0x00000000004172c9 in _start ()