(gdb) bt
#0  0x407daef1 in kill () from /lib/libc.so.6
#1  0x404bcbb1 in pthread_kill () from /lib/libpthread.so.0
#2  0x404bcf2b in raise () from /lib/libpthread.so.0
#3  0x407dab24 in raise () from /lib/libc.so.6
#4  0x407dc3fd in abort () from /lib/libc.so.6
#5  0x4080d76c in __libc_message () from /lib/libc.so.6
#6  0x40816066 in malloc_printerr () from /lib/libc.so.6
#7  0x40814d2f in _int_free () from /lib/libc.so.6
#8  0x4081394f in free () from /lib/libc.so.6
#9  0x08413a0c in ARDOUR::AudioExportSpecification::clear
(this=0x8d944f0)
    at libs/ardour/session_export.cc:134
#10 0x08414c52 in ARDOUR::Session::stop_audio_export (this=0x8923ea0, 
    spec=@0x8d944f0) at libs/ardour/session_export.cc:436
#11 0x081c3e61 in ExportDialog::end_dialog (this=0x8d93e88)
    at gtk_ardour/export_dialog.cc:1303
#12 0x081c20c4 in ExportDialog::do_export (this=0x8d93e88)
    at gtk_ardour/export_dialog.cc:1055
#13 0x081c5d48 in SigC::ObjectSlot0_<void, ExportDialog>::callback (
    d=0x8d856cc) at object_slot.h:56
#14 0x0806ed89 in SigC::Callback0<void>::call (this=0x8d856cc) at
slot.h:260
#15 0x0806ed70 in Gtk::ProxySignal0<void, Gtk::Button, _GtkButton,
2>::gtk_callback (d=0x8d856e0) at proxy.h:90
#16 0x401ea877 in gtk_marshal_NONE__NONE () from
/usr/lib/libgtk-1.2.so.0
#17 0x40219e5a in gtk_signal_remove_emission_hook ()
   from /usr/lib/libgtk-1.2.so.0
#18 0x4021916a in gtk_signal_set_funcs () from
/usr/lib/libgtk-1.2.so.0
#19 0x40217234 in gtk_signal_emit () from /usr/lib/libgtk-1.2.so.0
#20 0x40189e1c in gtk_button_clicked () from /usr/lib/libgtk-1.2.so.0
#21 0x4018b38a in gtk_button_get_relief () from
/usr/lib/libgtk-1.2.so.0
#22 0x084b51fd in Gtk::Button::released_impl (this=0x8d94350)
    at libs/gtkmm/src/gtk--/button.cc:175
#23 0x084b517b in Gtk::Button_Class::released_callback (o_=0x8d8a098)
    at libs/gtkmm/src/gtk--/button.cc:157
#24 0x401ea877 in gtk_marshal_NONE__NONE () from
/usr/lib/libgtk-1.2.so.0
#25 0x4021907b in gtk_signal_set_funcs () from
/usr/lib/libgtk-1.2.so.0
#26 0x40217234 in gtk_signal_emit () from /usr/lib/libgtk-1.2.so.0
#27 0x40189d60 in gtk_button_released () from /usr/lib/libgtk-1.2.so.0
#28 0x4018ad26 in gtk_button_get_relief () from
/usr/lib/libgtk-1.2.so.0
---Type <return> to continue, or q <return> to quit---
#29 0x084f6a94 in Gtk::Widget::button_release_event_impl
(this=0x8d94350, 
    p0=0x88fa968) at libs/gtkmm/src/gtk--/widget.cc:1534
#30 0x084f69f6 in Gtk::Widget_Class::button_release_event_callback (
    o_=0x8d8a098, p0=0x88fa968) at libs/gtkmm/src/gtk--/widget.cc:1514
#31 0x084cfb4f in gtkmm_marshal_INT__POINTER (object=0x8d8a098, 
    func=0x84f69be
<Gtk::Widget_Class::button_release_event_callback(_GtkWidget*,
_GdkEventButton*)>, func_data=0x0, args=0xbfffefb0)
    at libs/gtkmm/src/gtk--/marshal.cc:240
#32 0x4021919f in gtk_signal_set_funcs () from
/usr/lib/libgtk-1.2.so.0
#33 0x40217234 in gtk_signal_emit () from /usr/lib/libgtk-1.2.so.0
#34 0x4024cfd9 in gtk_widget_event () from /usr/lib/libgtk-1.2.so.0
#35 0x401ea4d0 in gtk_propagate_event () from /usr/lib/libgtk-1.2.so.0
#36 0x401e95c1 in gtk_main_do_event () from /usr/lib/libgtk-1.2.so.0
#37 0x40291b44 in gdk_wm_protocols_filter () from
/usr/lib/libgdk-1.2.so.0
#38 0x402bfe75 in g_get_current_time () from /usr/lib/libglib-1.2.so.0
#39 0x402c032c in g_get_current_time () from /usr/lib/libglib-1.2.so.0
#40 0x402c055c in g_main_run () from /usr/lib/libglib-1.2.so.0
#41 0x401e9083 in gtk_main () from /usr/lib/libgtk-1.2.so.0
#42 0x084ce26f in Gtk::Main::run_impl (this=0x86f0460)
    at libs/gtkmm/src/gtk--/main.cc:11
#43 0x0806f9c1 in Gtk::Main::run () at main.h:168
#44 0x0846a8da in Gtkmmext::UI::run (this=0x86f19d0,
old_receiver=@0x86dab80)
    at libs/gtkmmext/gtk_ui.cc:171
#45 0x08239b8a in main (argc=1, argv=0xbffff5b4) at
gtk_ardour/main.cc:484