fedora, rhn, bad public key?

Have any other fedora users run into failures while trying to update
their system through RHN up2date?

The majority of the packages I retrieve give me a "bad key" error and
say the package is corrupt or has been tampered with.

I've been using apt as an alternative (I don't receive these errors when
I use apt) but this can be a bit of a pain since the kernel
build-version I want isn't available (athlon).

Any ideas/thoughts?

Thx,
Bart