Olivier Galibert <galibert(a)pobox.com> writes in xemacs-beta(a)xemacs.org:
Are your generated PNGs compatible with previous libpng versions?
I don't know. I thought so.
The one you usually attach to your mails are rejected by the locally
installed xv (libpng 0.99, png.h says).
Uh oh. Does xmine/PNG work for you?