Also, just wanted to add that I don't have this issue with my old camera (Nikon D700). CS4 was able to read those RAW files, and when I made my star ratings in PM, I can see the ratings.
With my new camera (Nikon DF), CS4 can no longer read the RAW files, which shouldn't be a big deal, because I can cull in PhotoMechanic. But for some reason, it's just the ratings not following through on those images. When those same RAW files are changed to DNG's and starred, suddenly I can see the ratings showing up in Bridge CS4.