Photoshop CS6 footage stuttering

Im trying to edit clips on Photoshop CS6 but they keep stuttering.
Im using Macbook Pro late 2011 with 16GB Ram, i7.
The clips play fine in lightroom, adobe premier pro and Quicktime.
I've been searching the web for an answer but cannot seem to be able to find anything of use.
Im editing .mov clips from Nikon D600.

Any tips to solve this problem would be greatly appreciated.
Thanks

I know this may be obvious, but what is the end resulting file size? If it is to large, sometimes the read speed of the hard drive can't keep up, and makes it stutter, depending on the type of hard drive installed. Sometimes try reducing the quality of the photo jpeg and run a test. That has been my experience.

Otherwise, post your render/export settings so we can take a look if you got everything correct.

Thanks for your prompt reply Physics. The file size of the clip is 76MB, the files are store on a WD external drive, but I had the same problem when I tried to play them on a thunderbolt drive.
I have given Photoshop Cs6 12GB of Ram to use.
At the moment I am just trying to play the clips in Photoshop Cs6, I am not trying to render or export them.
Something I have noticed - in the timline box in red writing is the play level is failing to reach 24fps, its jumping all over the place but not getting to 24fps.
How can I make it play at 24fps as I thought as doubling the Ram to 16gb would help.
Thanks.

I don't use PS to edit, I use AE, so this is going to be some guess work. One thing I noticed is that if I edit from an external drive, if there is less data on it, it works better. If it is a disk drive (not solid state) it will take longer to seek data, and play back video stuttery if it is very full.

In after effects, RAM is for prerendering video, but processor power is what plays video in real time, so I don't think that increase of RAM will help.

It could be that your editor is just skipping and if you export the video it will play fine. I would really try to invest in AE or Premiere for video editing, unless PS is already key to your work flow.

Hope that helps, I am not a PS guy so that is the best I can do.

Thanks for your reply.
Ive ruled out external hard drive as the same thing happens on my new $500 thuderbolt drive!
So the only thing I can imagine is causing this is the graphics card which is AMD Radeon HD 6750M 512 MB graphics! Maybe 1GB of ram will solve the problem.
So I will have to edit on another platform.
In Premiere Pro I cannot see where you edit contrast and retouch dirt is that all done in After Effects?