This issue can be reproduced on Linux x86_64 and Windows MinGW 32-bit.
The crash occurs everytime, it renders Glade unusable.

Description
- SEGV when adding a new top-level GtkDialog to an empty project
- SEGV when adding a GtkComboBox
- SEGV when loading a GtkBuilder .ui definition containing any composed widgets

Analysis

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7dabe41 in glade_widget_set_object (gwidget=0x8a3620, 
    new_object=0x10d3820, destroy=1) at glade-widget.c:3359
3359		g_return_if_fail (new_object == NULL || 
			  g_type_is_a (G_OBJECT_TYPE (new_object),
				       gwidget->adaptor->type));


Glade-3 crashes during creation of the GtkDialog's internal GtkVBox 
because gwidget->adaptor is NULL

The creation of the 'adaptor' can be tracked down to frame #3 (see stack
trace below). It gets lost somewhere in Frame #2,#1,#0

Looks like a problem with the custom widget constructor methods of GLib.

The following GLib versions have been checked:
- GLib 2.34.3 - no crash
- GLib 2.35.7 - no crash
- GLib 2.36.x - not tested
- GLib 2.37.1 - SEGV

When creating different composed widgets, the stack trace looks very similar  and always ends up at the same location at glade-widget.c:3359 

Adding an additional check for (gwidget->adaptor != NULL) doesn't help, it will crash later at different locations.

Stack trace

+ Trace 232129

Additional Glade-3 debug output:

$ gdb glade-3
GNU gdb (GDB) Red Hat Enterprise Linux (7.2-60.el6_4.1)
Copyright (C) 2010 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-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /opt/casy/gtk/.Linux.3.x86_64/bin/glade-3...done.
(gdb) r

Starting program: /opt/casy/gtk/.Linux.3.x86_64/bin/glade-3 
warning: no loadable sections found in added symbol-file system-supplied DSO at 0x7ffff7ffd000
[Thread debugging using libthread_db enabled]

(glade-3:5648): GladeUI-WARNING **: Failed to open catalog directory '': Error opening directory '': No such file or directory

(glade-3:5648): GladeUI-WARNING **: Failed to open catalog directory '': Error opening directory '': No such file or directory
GladeUI-Message: No displayable values for property GtkToolPalette::icon-size
GladeUI-Message: No displayable values for property GtkToolItemGroup::ellipsize
GladeUI-Message: No displayable values for property GtkToolItemGroup::header-relief

(glade-3:5648): GladeUI-WARNING **: Already registered displayable value None for none (type GtkSelectionMode)

(glade-3:5648): GladeUI-WARNING **: Already registered displayable value Single for single (type GtkSelectionMode)

(glade-3:5648): GladeUI-WARNING **: Already registered displayable value Browse for browse (type GtkSelectionMode)
GladeUI-Message: 2 missing displayable value for GtkSheet::selection-mode
GladeUI-Message: No displayable values for property GtkSheet::entry-type
GladeUI-Message: No displayable values for property GtkSheet::vjust
GladeUI-Message: No displayable values for property GtkSheetColumn::entry-type
GladeUI-Message: No displayable values for property GtkSheetColumn::vjust
GladeUI-Message: Glade needs artwork; a default icon will be used for the following classes:
	GtkPlotData	needs an icon named 'widget-gtkextra-gtkplotdata'
	GtkPlotCanvasEllipse	needs an icon named 'widget-gtkextra-gtkplotcanvasellipse'
	GtkPlotCanvasRectangle	needs an icon named 'widget-gtkextra-gtkplotcanvasrectangle'
	GtkPlotPS	needs an icon named 'widget-gtkextra-gtkplotps'
	GtkPlotSurface	needs an icon named 'widget-gtkextra-gtkplotsurface'
	GtkPlotCanvasLine	needs an icon named 'widget-gtkextra-gtkplotcanvasline'
	GtkPlotArrayList	needs an icon named 'widget-gtkextra-gtkplotarraylist'
	GtkPlotSegment	needs an icon named 'widget-gtkextra-gtkplotsegment'
	GtkDirTree	needs an icon named 'widget-gtkextra-gtkdirtree'
	GtkPlotPC	needs an icon named 'widget-gtkextra-gtkplotpc'
	GtkPlotArray	needs an icon named 'widget-gtkextra-gtkplotarray'
	GtkPlotDT	needs an icon named 'widget-gtkextra-gtkplotdt'
	GtkPlotCanvasPlot	needs an icon named 'widget-gtkextra-gtkplotcanvasplot'
	GtkPlotCanvasPixmap	needs an icon named 'widget-gtkextra-gtkplotcanvaspixmap'
	GtkPlotBar	needs an icon named 'widget-gtkextra-gtkplotbar'
	GtkPlotCanvasText	needs an icon named 'widget-gtkextra-gtkplotcanvastext'
	GtkPlotGdk	needs an icon named 'widget-gtkextra-gtkplotgdk'
	GtkPlotCSurface	needs an icon named 'widget-gtkextra-gtkplotcsurface'
	GtkPlotCanvasChild	needs an icon named 'widget-gtkextra-gtkplotcanvaschild'
	GtkDataEntry	needs an icon named 'widget-gtkextra-gtkdataentry'
GladeUI-Message: No DevHelp installed on your system, devhelp feature will be disabled.
[New Thread 0x7fffeb039700 (LWP 5682)]
[New Thread 0x7fffea838700 (LWP 5683)]
[New Thread 0x7fffea037700 (LWP 5685)]
[New Thread 0x7fffe9836700 (LWP 5686)]
[New Thread 0x7fffe9035700 (LWP 5688)]
[Thread 0x7fffe9035700 (LWP 5688) exited]
[Thread 0x7fffea838700 (LWP 5683) exited]
[Thread 0x7fffeb039700 (LWP 5682) exited]

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7dabe41 in glade_widget_set_object (gwidget=0x8a3620, 
    new_object=0xfe2050, destroy=1) at glade-widget.c:3359
3359		g_return_if_fail (new_object == NULL ||