Error: ... correct GPG keys installed?

[beartooth]

On at least one machine whose yum.conf used to work fine, I keep getting :
                         =====
Error: You may also check that you have the correct GPG keys installed
                         =====
whenever I try to run yum update.

It's Clint's sample file, which I don't *think* I recall touching, unless
maybe to comment out one or two of the first things that seemed to be
producing this. I did get GPG errors at first, until he kindly told me how
to fix them. What has changed, and how do I cope?

-- 
Beartooth Implacable, Linux Evangelist & Gadfly
neo-redneck, curmudgeonly codger with FC1 & YDL 4.0
Pine 4.61, Pan 0.14.2; Privoxy 3.0.1; Opera 7.54, Firefox 1.0
Bear in mind that I have little idea what I am talking about.