Changing the contents of a scrolled window?

[<veh zeal net>]

Hello
  
Hopefully, someone has done this before, and there is an easy solution
to this problem:
  
I have a scrolled window, in which i wish to show either a tree, or a 
clist.  Initially, I add the tree to the scrolled window with:
  
   gtk_scrolled_window_add_with_viewport(GTK_SCROLLED_WINDOW(window),
  					browsertree);
  
Everything works fine.  But then, i wish to remove the tree from the
window and replace it with a clist.  I have tried adding the clist
without first destroying the tree,  and i have tried various ways
of using "gtk_widget_destroy" to remove either the tree, or the 
whole scrolled window.  All i endup achieving is a seg. fault, and
then a core dump.  
  
How should i remove the tree from the scrolled window?  Any help
would be much appreciated.  Thanks.
  
-james