gtk2.2 pixbuf doesn't load any png file

Hi, all,

I am trying to build Gnome 2.2 on plain redhat 8.0
from the SRPM's. I have built and installed gtk2-2.2.1.
When I was build libgnomeui-2.2.0.1, I got err with message

failed to load "./stock_attach.png": Couldn't recognize the image file
format for file './stock_attach.png'

It turns out that gdk-pixbuf-csource doesn't work on
any .png file.

/etc/gtk-2.0/gdk-pixbuf.loaders
is an empty file and 
in directory /usr/lib/gtk-2.0/2.2.0/loaders
I can see that all the loader libs are installed correctly.

So my question is how to make the correct gdk-pixbuf.loaders
file for gdk-pixbuf-csource ?

Thanks a lot,

Xiong Jiang