I have an FC4 system on which I've installed some rpms from fedora-test. I turned on the nightly update yum but it never does anything. I left the mirror-style repos settings in there, the only change I made in the /etc/yum.repos/* files was to change enabled to 1. I administer 4 machines that are all about the same hardware and OS, and on one or two of them, the updates will be found & installed, but not the others. There are no errors in /var/log/*.
How can I troubleshoot this?