sweep application, GTK errors

[Christoph Kukulies <kuku gilberto physik rwth-aachen de>]

gtk-1.2.8:

I built Sweep, a sound editing tool.and I got the following when I started it, resp. when I tried to open a 
sound file:

Gtk-WARNING **: invalid cast from (NULL) pointer to `GtkObject'

Gtk-CRITICAL **: file gtksignal.c: line 724 (gtk_signal_connect): assertion `object != NULL' failed.
  
Any clues where to look. Who do I have top blame: Gtk or the application?

-- 
Chris Christoph P. U. Kukulies kuku gil physik rwth-aachen de