gtk combo trouble

[Enrico Borrione <devel seac02 it>]

hi all, 
i have got a problem with a gtk combo. It is piloted via a couple of
radio buttons.The combo should keep track of two separate album lists,
one for videos and one for images. My problem is this:

if the image album list is empty, my combo keeps being empty -> correct

if i switch to video list (not empty) my combo fills with the movie list
->correct

when i switch back to the image empty list, the combo remains filled
with the video list -> NOT correct...

my code is like:

void on_radiobutton1_toggled (GtkToggleButton *togglebutton, gpointer
user_data){
LoadAlbumList(0,1);
gtk_combo_set_popdown_strings (GTK_COMBO (combo1), album_glist);
album_glist=NULL;
gtk_widget_show (combo_entry1);
}
                                                                                
void on_radiobutton2_toggled (GtkToggleButton *togglebutton, gpointer
user_data){
LoadAlbumList(0,0);
gtk_combo_set_popdown_strings (GTK_COMBO (combo1), album_glist);
album_glist=NULL;
gtk_widget_show (combo_entry1);
}

LoadAlbumList returns the GList pointer called album_glist. If the list
is empty, then album_glist is set to NULL. I was thinking that setting
the pop_down_strings to NULL would empty the combo, but probably i am
wrong...

anyone can help me?