5D MkIII & Halos on Image Quality Settings

I've had my 5d MkIII for a few months now. I had read about the "halo" effect with the highest settings on quality. I have experienced this myself sometimes. Has anyone else seen this happen? I use the 24 - 105 L series IS lens. I've read about some users setting the quality on M and it is ok. My previous camera was the first generation 5D. I did 1,000s of shots with it with no halo effect. Any comments? Love this new camera but you would think Canon wouldn't have this problem.