Assertion from gtk_notebook_append_page

["Ian" <ian underpressuredivers com>]

Any ideas on this one?

I'm getting this printed on every call to add a page to a GtkNotebook,
although the pages are added OK and the notebook displays fine:

(hcpgui.exe:3628): Gtk-CRITICAL **: gtk_container_foreach: assertion
`GTK_IS_CONTAINER (container)' failed

The assertions are printed when gtk_notebook_append_page is called in the
following sequence:

  viewWin = gtk_scrolled_window_new(NULL, NULL);
  .
  noteBook = gtk_notebook_new();
  lbl = gtk_label_new("some text");
  gtk_notebook_append_page(GTK_NOTEBOOK(noteBook), viewWin, lbl);

Ian