My first question is why are you converting to DNG before importing into Aperture? It appears that Aperture should support the RAW files from that camera.
Second question is how familiar are you with the whole concept of RAW images? You realize that none of the camera settings (apart from shutter speed and aperture) affect the digital RAW file.
One of the strengths and reasons for shooting RAW is the ability to adjust white balance after the shoot. JPG images are extremely limited in their ability to have there white balance adjusted.
RAW conversion software is as much art as science, which is why no two RAW conversion programs will render an image in exactly the same way.
So I would first eliminate the DNG step and then see how that affects the workflow.
Frank - perhaps I have not been as clear as I might have been.
First - my camera, Pentax K-5, has two native RAW formats, PEF and DNG, I use DNG. There is no "conversion" to DNG step, I am loading RAW files direct from camera to Aperture.
Second - when Aperture imports a RAW file, it reads the white balance (amongst other) settings from the RAW header file and uses those to apply initial white balance settings to the converted RAW file.
My question is, why am I seeing variations in these initial white balance settings in a set of photographs where the camera settings were static? Is this variation a camera isssue or a RAW conversion issue?
You'll always get minor differences in the WB values after the RAW conversion as no two images are exactly alike unless you're shooting in a laboratory setup with everything totally controlled, down to the frequency of the AC feeding your lighting.
With any lighting setup, natural or artificial, there will be minor changes from shot to shot. We may not perceive these but the RAW conversion SW does and that is what accounts for the differences.
If you can get your hands on another RAW converter, there are many out there and some offer free trials, you should. You'll be amazed at the variations form one to the another.