I didn't -- but I do now (actually, just for the record, it seems that kgpg is a separate RPM from all the other kdeutils, presumably for legal reasons).
Anyway, unfortunately, it makes no difference. Kpgp can see my keys just fine, including the secret key. But the dialogue in Kopete is still empty.
I wonder where Kopete is looking for the key? Obviously, it's not looking in the right place. I have a couple of other GPG-aware programs and they can find the secret key just fine.