David, this seems very odd. I have never had any trouble with kills not being reported when I have landed on concrete at a friendly base. As a matter of fact, i've actually landed a couple in the middle of Vehicle bases in aircraft that were on fire and still had a kill report come up. (this is a bug though and happens from time to time)
I know this might sound stupid, but trying going to F3 view before you end sortie and make sure that your entire aircraft is on the runway.
(You can land anywhere as long as it's concrete, but let's just stick with the runway for now)
It doesn't matter what condition your aircraft is in, rubber side down or whatever... as long as you're alive and your aircraft is on the concrete, it's a 'successfull' landing.
If this does not solve your problem, hit Alt + R to start recording a film. Land and if the kills do not show up, press Alt + R again to stop recording, go to your HTC folder - > Films and get the film and post it here for HTC or us to have a look at.