Halo render problems on Mac

I have a scene with a single Halo (as the Sun) and find that the Halo flickers in brightness randomly (but consistently on the same frames).
I have rendered the same .blend on PC and this error doesn’t exist.
I am running a Mac Pro Quad Intel xeon with 4gb Mem, and Blender 2.47 (2.46 did the same). Has anyone seen Halo render problems on Macs before?

Have you tried with v2.48? If the bug’s still there in 2.48, it’s probably an idea to submit it to the bug tracker.