libglade warning - unknown widget class GtkComboBox

["Matthew Yaconis" <myaconis nycap rr com>]

I've run into some difficulty with libglade and I'm not sure how to fix it.  I had an old glade file 
(mainwin.glade) that I was using to generate gtk+1.2 code.  I used the libglade-convert function to bring it 
up to the glade 2.6.0 level. Then I edited the file some, removing option menus and other deprecated widgets, 
replacing them with combo boxes and such.  I also added other glade 2.6.0 generated files to my baseline for 
other windows I needed to create.  Originally, I used glade to generate the interface.[ch] files for 
mainwin.glade, but since I had to change all my calls to gtk_object_get_data to conform with gtk 2.4.X, I 
decided to chuck the glade generated source and use libglade instead.  However, now when I run my program I 
get the following warning for my combo boxes and the widgets don't appear in the window:

(dva:5177): libglade-WARNING **: unknown widget class 'GtkComboBox'

The wierd part about this is in the files I generated with glade 2.6.0 I don't get a warning like this for 
the combo boxes and they work just fine.  I compared the two files for differences and couldn't find any of 
consequence...but I haven't inspected glade SGML before so I'm probably missing something.

Any ideas?  

I build with 

pkg-config --cflags gtk+-2.0 libglade-2.0
pkg-config --libs gtk+-2.0 libglade-2.0