Using gnome_druid_set_buttons_sensitive works fine for me...
Code:
GtkWidget *gnomedruid1=NULL;
GladeXML *gxml=NULL;
/* get druid from glade XML file */
gxml = glade_xml_new ("gui.glade", NULL, NULL);
gnomedruid1 = glade_xml_get_widget (gxml, "gnomedruid1");
/* disable "forward" button-- only "cancel" is enabled */
gnome_druid_set_buttons_sensitive (GNOME_DRUID(gnomedruid1),
FALSE, /* back button */
FALSE, /* next button */
TRUE, /* cancel button */
FALSE ); /* help button */
void
gnome_druid_set_buttons_sensitive ( GnomeDruid *druid,
gboolean back_sensitive,
gboolean next_sensitive,
gboolean cancel_sensitive,
gboolean help_sensitive);