gtk and window size

[Matt Eisemann <meisemann dsrnet com>]

Currently I am building an application which has many nested vetical and 
horizontal boxes and I am trying to figure out if a parent box overrides 
the parameters set by a child box.  It looks like it does if you want a 
parent box to be nonhomogeneous and a child to be homogenious and visa 
versa.  My actual question is in regard to a CLIST.  In my application I 
have a CLIST in a scrolled window.  How do you set the default size of a 
scrolled window so that a user can adjust its size?  If one uses 
gtk_widget_set_usize it will set the size correctly but it seems to be 
static and unmovable by the user and it prevents the user from being able 
to expand the size of the scrolled window and hence the CLIST.  The 
function I was thinking of using was gtk_window_set_default_size but I get 
some strange error messages

Gtk-CRITICAL ** file gtkwindow.c: line 809 (gtk_window_set_default_size): 
assertion 'GTK_IS_WINDOW (window)' failed.

The code for my window where I put my CLIST is.

scrolled_win = gtk_scrolled_window_new(NULL,NULL)
gtk_window_set_default_size(scrolled_win,400,400);
gtk_container_add(GTK_CONTAINER(scrolled_win),display_tasks);

where display_tasks should be the CLIST.

Any ideas?  Let me know if you need more code or a better explanation of 
something.  Thanks ahead of time for your help.

Matt