Lightroom version: CC 01.01.2015 
Operating System: Mac OS 10
Version: 10.10 
Views: 1) 2560 x 1440
Information on the GPU:
AMD Radeon HD 6970M OpenGL engine
After importing photos and videos (.mts, .mp4, .mov)
I can see thumbnails of this videos; we can see the differents images when I mobilize the cursor over it;
If I want to see them, I double-clicked;
I got a white window with the following error message:
"An error occurred while working on the video"
there is no icon to begin playback; no way to see this video .
With the same catalog on another computer, Mac Book, I do not have this problem ... Videos are visible.
"you got it working with mc book that will answer me ..."
But I must not viewing comfort of the 27 inch screen!
Thanks for your help.