libpng / gtk problems

["Chiu, PCM \(Peter\)" <P C M Chiu rl ac uk>]

We have a new problem in using gnome-session to fire up
a gnome session.  The session is started, but the icons
in the bottom menu bar disappear.

At the same time, a number of errors are reported on the screen
saying:

Window manager warning: Failed to load theme "Bluecurve":
line 230  character 28: 
couldn't recognise the image file format for file
'/usr/share/themes/Bluecurve/metacity-1/minimize.png'

and similar messages for other png files.

Did try to apply the latest updates on libpng, gtk-2.0 etc,
but no avail.

Any offer of idea?

The box is a dual Xeon 2.8GHz PC with 2GB RAM and running
RHEL AS 3 update 4.