After digging, it seems someone at ART had changed "VERSION="1.0-11" in atomic.sh to VERSION="1.0-12" but had forgotten to put "atomic-release-1.0-12.el5.art.noarch.rpm" into the repo.
Managed to get around it by creating and running a local version of atomic.sh which I got from the site after changing the version manually back to 1.0-11.
Seems Scott is human afterall
