I think I found one of my setup problems. I followed instructions at: http://atrpms.net/install.html
And now I see that the information shown there to put into yum.conf (that I put into yum.repo.d/atrpms.repo) is only for FC, not for RL5 (thus Centos 5).
What do I use in my atrmps.repo to get it to access the RL5 directories?