When I start LibreOffice with SAL_USE_VCLPLUGIN=gtk3,
The following error messages (as follows) are printed out, and none of windows are seen.
(Even if the experimental features are enabled, in advance)
It works correctly with SAL_USE_VCLPLUGIN=gtk.

Versions:
NetBSD 6.1
GTK 3.8.8
GLib: 2.36.4

build options:
./configure --prefix=/usr/local --disable-fetch-external --disable-epm --disable-odk --enable-python=system --enable-gtk3 --enable-dbus --enable-gio --disable-neon --without-fonts --without-afms --with-system-cairo --with-system-nss --with-system-zlib --with-system-openssl --with-system-jpeg --with-system-expat --with-system-libwpd --with-system-libwps --with-system-libwpg --with-system-libxml --with-system-icu --with-system-poppler --with-system-mesa-headers --with-system-curl --with-system-boost --with-system-lpsolve --with-system-libexttextcat --with-system-cppunit --with-system-redland --with-system-libpng --without-java --without-krb5 --without-gssapi --with-lang=ja --with-system-lcms2 --with-system-hunspell --disable-gnome-vfs --disable-gstreamer-0-10 --enable-gstreamer --with-system-harfbuzz --with-system-ucpp --disable-firebird-sdbc --enable-release-build --with-vendor=FURUBAYASHI Yutaka --disable-opencl --enable-pch

Error messages:
(soffice:23261): Gtk-CRITICAL **: void gtk_style_context_set_path(GtkStyleContext *, GtkWidgetPath *): assertion `priv->widget == NULL' failed
allocated m_aFrame size of 1251x718 
allocated m_aFrame size of 1251x718 
font name BEFORE system match: "ヒラギノ角ゴ StdN"
font match succeeded, name AFTER: "W2"
** (soffice:23261): WARNING **: no get work area

** (soffice:23261): WARNING **: no get work area
Unhandled is native supported for Type: 150, Part 6000
Unhandled is native supported for Type: 131, Part 1
allocated m_aFrame size of 1366x717 
font name BEFORE system match: "ヒラギノ角ゴ StdN"
font match succeeded, name AFTER: "W2"

** (soffice:23261): WARNING **: no get work area

** (soffice:23261): WARNING **: no get work area
Unhandled is native supported for Type: 150, Part 6000
Unhandled is native supported for Type: 131, Part 1
Unhandled is native supported for Type: 120, Part 250
Unhandled is native supported for Type: 120, Part 1
Unhandled is native supported for Type: 120, Part 1
Unhandled is native supported for Type: 160, Part 7000
Unhandled is native supported for Type: 160, Part 7000
Unhandled is native supported for Type: 160, Part 7000
Unhandled is native supported for Type: 160, Part 7000
Unhandled is native supported for Type: 160, Part 7000
Unhandled is native supported for Type: 160, Part 7000
Unhandled is native supported for Type: 160, Part 7000
Unhandled is native supported for Type: 160, Part 7000

(soffice:23261): GLib-GObject-WARNING **: cannot register existing type `GtkImageType'

(soffice:23261): GLib-GObject-CRITICAL **: GParamSpec *g_param_spec_enum(const gchar *, const gchar *, const gchar *, GType, gint, GParamFlags): assertion `G_TYPE_IS_ENUM (enum_type)' failed

(soffice:23261): GLib-GObject-CRITICAL **: void g_object_class_install_property(GObjectClass *, guint, GParamSpec *): assertion `G_IS_PARAM_SPEC (pspec)' failed

(soffice:23261): GLib-GObject-WARNING **: cannot register existing type `GdkScreen'

(soffice:23261): GLib-CRITICAL **: void g_once_init_leave(volatile void *, gsize): assertion `result != 0' failed

(soffice:23261): GLib-GObject-CRITICAL **: GParamSpec *g_param_spec_object(const gchar *, const gchar *, const gchar *, GType, GParamFlags): assertion `g_type_is_a (object_type, G_TYPE_OBJECT)' failed

(soffice:23261): GLib-GObject-CRITICAL **: void g_object_class_install_property(GObjectClass *, guint, GParamSpec *): assertion `G_IS_PARAM_SPEC (pspec)' failed

(soffice:23261): GLib-GObject-WARNING **: cannot register existing type `GtkOrientation'

(soffice:23261): GLib-GObject-CRITICAL **: GParamSpec *g_param_spec_enum(const gchar *, const gchar *, const gchar *, GType, gint, GParamFlags): assertion `G_TYPE_IS_ENUM (enum_type)' failed

(soffice:23261): GLib-GObject-CRITICAL **: void g_object_class_install_property(GObjectClass *, guint, GParamSpec *): assertion `G_IS_PARAM_SPEC (pspec)' failed

(soffice:23261): GLib-GObject-CRITICAL **: GType g_boxed_type_register_static(const gchar *, GBoxedCopyFunc, GBoxedFreeFunc): assertion `g_type_from_name (name) == 0' failed

(soffice:23261): GLib-GObject-WARNING **: gsignal.c:1643: parameter 1 of type `<unknown>' for signal "GtkStatusIcon::button_press_event" is not a value type

(soffice:23261): GLib-GObject-WARNING **: gsignal.c:1643: parameter 1 of type `<unknown>' for signal "GtkStatusIcon::button_release_event" is not a value type

(soffice:23261): GLib-GObject-WARNING **: gsignal.c:1643: parameter 1 of type `<unknown>' for signal "GtkStatusIcon::scroll_event" is not a value type

(soffice:23261): GLib-GObject-WARNING **: cannot register existing type `GtkTooltip'

(soffice:23261): GLib-CRITICAL **: void g_once_init_leave(volatile void *, gsize): assertion `result != 0' failed

(soffice:23261): GLib-GObject-WARNING **: gsignal.c:1643: parameter 4 of type `<invalid>' for signal "GtkStatusIcon::query_tooltip" is not a value type

(soffice:23261): GLib-GObject-WARNING **: cannot register existing type `GtkWidget'

(soffice:23261): GLib-GObject-CRITICAL **: void g_type_add_interface_static(GType, GType, const GInterfaceInfo *): assertion `G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(soffice:23261): GLib-GObject-WARNING **: cannot register existing type `GtkBuildable'

(soffice:23261): GLib-GObject-CRITICAL **: void g_type_interface_add_prerequisite(GType, GType): assertion `G_TYPE_IS_INTERFACE (interface_type)' failed

(soffice:23261): GLib-CRITICAL **: void g_once_init_leave(volatile void *, gsize): assertion `result != 0' failed

(soffice:23261): GLib-GObject-CRITICAL **: void g_type_add_interface_static(GType, GType, const GInterfaceInfo *): assertion `G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(soffice:23261): GLib-GObject-CRITICAL **: GType g_type_register_static(GType, const gchar *, const GTypeInfo *, GTypeFlags): assertion `parent_type > 0' failed