Comment 6 for bug 425221

I confirm also this problem .
In my UI xml file I add the line : <property name="orientation">vertical</property> in each <object> tag who have the class attribute = "GtkVBox"
Example :
  <object class="GtkVBox" id="vbox10">
                            <property name="visible">True</property>
                            <property name="orientation">vertical</property>
                            <child>
                           ......
                            </child>
                           <child>
                           ......
                            </child>
                           <child>
                           ......
                            </child>
  </object >