I rate my images with 1 star. Then I select and open them in ACR and edit. After I click "done" some of the files are no longer rated. I have to go lookin the unlabeled files for the missing images. Then when I try to restar them--it won't let me give it a 1 star. I can give it another rating, and then after that it will let me rate it at a 1 star. This only occured when I switched to CS6 from CS3.
Some have no problems with ratings and others find they disappear, so don't have any solution. Be sure and wait a few seconds as it seems like it is not instantaneous, especially with video.