Was the original footage shot 24p with pulldown inserted? I am guessing not, and that it's actually 59.94 fields per second. The best conversion you can get going to 23.976 will be with hardware such as Teranex VC100. In software land, you can get pretty good results with Compressor, but you need to make sure you turn on the Optical Flow Motion Compensation. That is accessible using Frame Controls - turn Frame Controls ON and choose BEST for Retiming. That will allow Compressor to analyze the frames as a sequence, blend them together, and remove what it intelligently 'thinks' can be removed. The results can be extremely usable or just not, so it's good to choose a couple of short sections to test. If you need help designing an encoding preset, let me know.