I'm installing updates from
http://download.fedora.redhat.com/pub/fedora/linux/updates/testing/13/i386
(is that the wrong place to go?)
Right now it contains
gnome-icon-theme-2.30.1-2.fc13.noarch.rpm and
gnome-icon-theme-extras-2.30.1-1.fc13.noarch.rpm
and these two don't like each other, leads to a version clash.