tree widget not displaying

[Chris De Maeyer <chrisdm pandora be>]

Having difficulty with a tree widget, seems to be processed but doesn`t
display anything in my gui:

        vboxa0 = gtk_vbox_new (FALSE, 0);
        
        framea1 = gtk_frame_new (" Airport ");
        gtk_container_set_border_width (GTK_CONTAINER (framea1), 10);
        
        gtk_container_add (GTK_CONTAINER (vboxa0),framea1);
        labela = gtk_label_new (" Airport ");
        
        store = gtk_tree_store_new (N_COLUMNS,
                        G_TYPE_STRING,
                        G_TYPE_STRING);
        FillAirports(store);
        tree = gtk_tree_view_new_with_model (GTK_TREE_MODEL (store));
        g_object_unref (G_OBJECT (store));
        renderer = gtk_cell_renderer_text_new ();
        g_object_set (G_OBJECT (renderer),
                "foreground", "red",
                NULL);
        column = gtk_tree_view_column_new_with_attributes ("ID", renderer,
                        "text", ID_COLUMN,NULL);
        gtk_tree_view_append_column (GTK_TREE_VIEW (tree), column);
        renderer = gtk_cell_renderer_text_new ();
        column = gtk_tree_view_column_new_with_attributes ("Location",
renderer,
                        "text", NAME_COLUMN,NULL);
        gtk_tree_view_append_column (GTK_TREE_VIEW (tree), column);
        
        gtk_widget_show (tree);
        gtk_widget_show (renderer);
        gtk_widget_set_size_request(vboxa0,640,100);
        gtk_widget_show (vboxa0);
        gtk_widget_show (framea1);

and the tree composer function:

int fgk_ReadAirports(char *flyfile,GtkTreeStore *st)
{
        FILE *tmp;
        char str[256];
        char word2[32];
        int start,einde;
        
        GString *tok;
        
        if((tmp=fopen(flyfile,"r"))!=NULL) {
                while(!feof(tmp)) {
                        fgets(str,sizeof(str)-1,tmp);
                        
                        start = getDelimPos(str,' ',1);
                        einde = getDelimPos(str,' ',2);
                        memset(word2,0,32);
                        memcpy(word2,str+start,einde-start);
                        
                        tok = g_string_new(word2);
                        /*combo_airports_list=g_list_append (combo_airports_list,
tok->str);*/
                        GtkTreeIter iter1;  /* Parent iter */
                        
                        gtk_tree_store_append (st, &iter1, NULL);  /* Acquire a top-level
iterator */
                        gtk_tree_store_set (st, &iter1,
                                ID_COLUMN, tok->str,
                                NAME_COLUMN, "Donald E. Knuth",
                                -1);
                }
                fclose(tmp);
        } else {
                return(-1);
        }       
        return(0);      
}       

Any ideas or remarks why this widget is not working?