I am experiencing the same issue on an up-to-date Ubuntu 16.04 install.
It seems to happen randomly. Nautilus doesn't launch and gives the error previously reported if launched via command line. A restart fixes it temporarily.
(nautilus:18396): GLib-GIO-CRITICAL **: g_dbus_interface_skeleton_unexport: assertion 'interface_->priv->connections != NULL' failed
Could not register the application: Timeout was reached
I am experiencing the same issue on an up-to-date Ubuntu 16.04 install.
It seems to happen randomly. Nautilus doesn't launch and gives the error previously reported if launched via command line. A restart fixes it temporarily.
GNOME nautilus 3.14.3
Linux 4.4.0-45-generic
(nautilus:18396): GLib-GIO-CRITICAL **: g_dbus_ interface_ skeleton_ unexport: assertion 'interface_ ->priv- >connections != NULL' failed
(nautilus:18396): GLib-GIO-CRITICAL **: g_dbus_ interface_ skeleton_ unexport: assertion 'interface_ ->priv- >connections != NULL' failed
Could not register the application: Timeout was reached
(nautilus:18396): Gtk-CRITICAL **: gtk_icon_ theme_get_ for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
(nautilus:18396): GLib-GObject- WARNING **: invalid (NULL) pointer instance
(nautilus:18396): GLib-GObject- CRITICAL **: g_signal_ connect_ object: assertion 'G_TYPE_ CHECK_INSTANCE (instance)' failed
I tried killing/ending the nautilus process and the whole X/unity session froze.