Error "result != 0" occurs here:

#0  g_return_if_fail_warning (log_domain=0x35deeaf42e "GLib", 
    pretty_function=0x35deebd720 <__PRETTY_FUNCTION__.5590> "g_once_init_leave", 
    expression=0x35deebd661 "result != 0") at gmessages.c:800
#1  0x00000035f242cad8 in gdk_window_get_type () at gdkwindow.c:264
#2  0x00000035f242d129 in gdk_window_get_display (window=0x7fe096656cc0)
    at gdkwindow.c:2219

Error "GDK_IS_WINDOW (window)" occurs here:

#0  g_return_if_fail_warning (log_domain=0x35f245bdf3 "Gdk", 
    pretty_function=0x35f2461510 <__PRETTY_FUNCTION__.30164> "gdk_window_get_display", 
    expression=0x35f245c3ec "GDK_IS_WINDOW (window)") at gmessages.c:800
#1  0x00000035f242d164 in gdk_window_get_display (window=<optimized out>)
    at gdkwindow.c:2219
#2  gdk_window_get_display (window=0x7fe096656cc0) at gdkwindow.c:2217

After that, the trace looks the same for both cases:

#3  0x00000035f2458ef9 in gdk_x11_window_set_user_time (window=0x7fe096656cc0, 
    timestamp=<optimized out>) at gdkwindow-x11.c:3067
#4  0x00007fe0e3e1eb9d in SetUserTimeAndStartupIDForActivatedWindow (
    aWindow=<optimized out>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/widget/gtk2/nsWindow.cpp:1329
#5  nsWindow::NativeShow (this=0x7fe095b7b980, aAction=<optimized out>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/widget/gtk2/nsWindow.cpp:3938
#6  0x00007fe0e3e23087 in Show (aState=true, this=0x7fe095b7b980)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/widget/gtk2/nsWindow.cpp:997
#7  nsWindow::Show (this=0x7fe095b7b980, aState=true)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/widget/gtk2/nsWindow.cpp:948
#8  0x00007fe0e39944b4 in nsView::NotifyEffectiveVisibilityChanged (this=0x7fe099b3d080, 
    aEffectivelyVisible=true)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/view/src/nsView.cpp:479
#9  0x00007fe0e39944f3 in nsView::SetVisibility (this=0x7fe099b3d080, 
    aVisibility=<optimized out>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/view/src/nsView.cpp:495
#10 0x00007fe0e399597b in nsViewManager::SetViewVisibility (this=0x7fe0952fd510, 
    aView=0x7fe099b3d080, aVisible=nsViewVisibility_kShow)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/view/src/nsViewManager.cpp:1161
#11 0x00007fe0e37b3df1 in nsMenuPopupFrame::LayoutPopup (this=0x7fe09f4dcbf0, 
    aState=..., aParentMenu=<optimized out>, aSizedToPopup=<optimized out>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsMenuPopupFrame.cpp:455
#12 0x00007fe0e37b7d33 in nsPopupSetFrame::DoLayout (this=<optimized out>, aState=...)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsPopupSetFrame.cpp:122
#13 0x00007fe0e379d21b in nsIFrame::Layout (this=0x7fe09f4df020, aState=...)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsBox.cpp:510
#14 0x00007fe0e37a1a5f in nsSprocketLayout::Layout (this=0x7fe0bdb39cc0, 
    aBox=0x7fe09d710338, aState=...)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsSprocketLayout.cpp:488
#15 0x00007fe0e379e732 in nsBoxFrame::DoLayout (this=0x7fe09d710338, aState=...)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsBoxFrame.cpp:907
#16 0x00007fe0e379d21b in nsIFrame::Layout (this=0x7fe09d710338, aState=...)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsBox.cpp:510
#17 0x00007fe0e37a2b57 in nsStackLayout::Layout (this=<optimized out>, 
    aBox=0x7fe09d710140, aState=...)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsStackLayout.cpp:340
#18 0x00007fe0e379e732 in nsBoxFrame::DoLayout (this=0x7fe09d710140, aState=...)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsBoxFrame.cpp:907
#19 0x00007fe0e379d21b in nsIFrame::Layout (this=0x7fe09d710140, aState=...)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsBox.cpp:510
#20 0x00007fe0e379f07b in nsBoxFrame::Reflow (this=0x7fe09d710140, aPresContext=
    0x7fe09524e400, aDesiredSize=..., aReflowState=..., aStatus=@0x7fff64e392cc: 0)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/xul/base/src/nsBoxFrame.cpp:702
#21 0x00007fe0e36dab5f in nsContainerFrame::ReflowChild (this=<optimized out>, 
    aKidFrame=0x7fe09d710140, aPresContext=0x7fe09524e400, aDesiredSize=..., 
    aReflowState=..., aX=<optimized out>, aY=0, aFlags=0, aStatus=@0x7fff64e392cc: 0, 
    aTracker=0x0)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/generic/nsContainerFrame.cpp:907
#22 0x00007fe0e3725175 in ViewportFrame::Reflow (this=0x7fe09d70faf8, 
    aPresContext=0x7fe09524e400, aDesiredSize=..., aReflowState=..., 
    aStatus=@0x7fff64e392cc: 0)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/generic/nsViewportFrame.cpp:201
#23 0x00007fe0e36b1c3c in PresShell::DoReflow (this=0x7fe096f05bc0, 
    target=0x7fe09d70faf8, aInterruptible=true)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/base/nsPresShell.cpp:7447
#24 0x00007fe0e36b1ee0 in PresShell::ProcessReflowCommands (this=0x7fe096f05bc0, 
    aInterruptible=true)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/base/nsPresShell.cpp:7594
#25 0x00007fe0e36b220f in PresShell::FlushPendingNotifications (this=0x7fe096f05bc0, 
    aType=Flush_InterruptibleLayout)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/base/nsPresShell.cpp:3859
#26 0x00007fe0e36b5bbb in nsRefreshDriver::Notify (this=0x7fe0968a4400, 
    aTimer=<optimized out>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/base/nsRefreshDriver.cpp:395
#27 0x00007fe0e36b5d75 in nsRefreshDriver::Notify (this=<optimized out>, 
    aTimer=<optimized out>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/layout/base/nsRefreshDriver.cpp:306
#28 0x00007fe0e3f8ba11 in nsTimerImpl::Fire (this=0x7fe09404f6f0)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/xpcom/threads/nsTimerImpl.cpp:476
#29 0x00007fe0e3f8badf in nsTimerEvent::Run (this=<optimized out>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/xpcom/threads/nsTimerImpl.cpp:556
#30 0x00007fe0e3f88d72 in nsThread::ProcessNextEvent (this=0x7fe0e5527d80, 
    mayWait=false, result=0x7fff64e3966f)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/xpcom/threads/nsThread.cpp:624
#31 0x00007fe0e3f5e2ab in NS_ProcessNextEvent_P (thread=<optimized out>, mayWait=false)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/obj-x86_64-unknown-linux-gnu/xpcom/build/nsThreadUtils.cpp:217
#32 0x00007fe0e3ec19ae in mozilla::ipc::MessagePump::Run (this=0x7fe0e1b6a780, 
    aDelegate=0x7fe0e5578340)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/ipc/glue/MessagePump.cpp:82
#33 0x00007fe0e3fa5241 in RunHandler (this=0x7fe0e5578340)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/ipc/chromium/src/base/message_loop.cc:201
#34 MessageLoop::Run (this=0x7fe0e5578340)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/ipc/chromium/src/base/message_loop.cc:175
#35 0x00007fe0e3e3ae4c in nsBaseAppShell::Run (this=0x7fe0de48e780)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/widget/xpwidgets/nsBaseAppShell.cpp:163
#36 0x00007fe0e3d12b9e in nsAppStartup::Run (this=0x7fe0de4823d0)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/toolkit/components/startup/nsAppStartup.cpp:257
#37 0x00007fe0e35463b6 in XREMain::XRE_mainRun (this=0x7fff64e39948)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/toolkit/xre/nsAppRunner.cpp:3794
#38 0x00007fe0e35465ae in XREMain::XRE_main (this=0x7fff64e39948, argc=<optimized out>, 
    argv=0x7fff64e3bd28, aAppData=0x625820 <sAppData>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/toolkit/xre/nsAppRunner.cpp:3871
#39 0x00007fe0e35467aa in XRE_main (argc=1, argv=0x7fff64e3bd28, 
    aAppData=0x625820 <sAppData>, aFlags=<optimized out>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/toolkit/xre/nsAppRunner.cpp:3947
#40 0x0000000000402b20 in do_main (argv=0x7fff64e3bd28, argc=1)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/browser/app/nsBrowserApp.cpp:160
#41 main (argc=<optimized out>, argv=<optimized out>)
    at /var/tmp/portage/www-client/firefox-16.0.2/work/mozilla-release/browser/app/nsBrowserApp.cpp:265

The "GdkWindow *window" in frame #3 at address 0x7fe096656cc0 looks like this:
{parent_instance = {g_type_instance = {g_class = 0x7fe0e5577700}, ref_count = 3, 
    qdata = 0x7fe09f7cc1a0}, impl = 0x7fe094f94f60, parent = 0x7fe0e5549540, 
  visual = 0x7fe096656b80, user_data = 0x0, x = 0, y = 0, event_mask = 0, 
  filters = 0x7fe09f7cc0c0, children = 0xededefef00efede8, background = 0xe8e8, 
  paint_stack = 0x0, update_area = 0x0, update_freeze_count = 0, window_type = 0 '\000', 
  depth = 0 '\000', resize_count = 0 '\000', toplevel_window_type = 0 '\000', 
  state = (unknown: 0), guffaw_gravity = 0, input_only = 0, modal_hint = 1, 
  composited = 0, has_alpha_background = 0, destroyed = 0, accept_focus = 0, 
  focus_on_map = 0, shaped = 0, support_multidevice = 0, 
  synthesize_crossing_event_queued = 1, effective_visibility = 1, visibility = 0, 
  native_visibility = 0, viewable = 0, applied_shape = 0, impl_window = 0xc000000001, 
  update_and_descendants_freeze_count = 64514, abs_x = 0, abs_y = 0, width = 0, 
  height = -1771737920, clip_region = 0x0, clip_region_with_children = 0xc8000000c8, 
  layered_region = 0x374, cursor = 0x7fe0954deca0, device_cursor = 0x7fe0954de070, 
  implicit_paint = 0x0, outstanding_moves = 0x16ff, shape = 0x0, input_shape = 0x0, 
  cairo_surface = 0x0, devices_inside = 0x0, device_events = 0x0, 
  source_event_masks = 0x0, device_added_handler_id = 0, device_changed_handler_id = 0, 
  num_offscreen_children = 6488161}