Movies are normally stored at 23,976Hz. A very limited number have been mastered in 24,000Hz but they are certainly quite rare. Thats it.
Movier reported as 23,98 is propbably youre "reading" program rounding it off(from 23,976). Movies reported as 29,97 is after reverse telcine effctively made into its 23,976Hz original.
Judder with ATI has more to do with drivers. Nvidia can get it right but not ATI. Their 23 setting in CCC constantly deviates (23,974-23,977) during playback, resulting in occasional judders here and there.
Set it at 24 (which for some reson does not deviate, rock solid at 24,001 in my case) and get reclock. Otherwise buy nvidia.