GPG signature unknown

[Hacksaw]

Boy, I'm not having a good week. Yesterday my monitor died. Given it
was six years old, but I had hoped for a little longer life from it. 

But here's today's irritation:

I was trying to upgrade glibc, in the hopes that this might solve my X
woes.

It goes through the dependencies checking and what not, and then
reports that one of the packages has an unknown GPG signature.

I stopped the install.

I have run into this on initscripts as well.

Is it the repository? Is it someone in redhat screwing up? Is there
some package or configuration I have failed to get right? What's
going on here?

I am this far -> <- from throwing out FC3. This is sad because I was
looking towards using it at a client site, who is in desparate need of
an upgrade, as they are running RH 6.2. I kid you not.