I am new to Lr this year. Using Mac. Have imported photos in Lr, and have put some of them into Collection, and some videos among them, It worked well, but only for a short time. Then the video would not work any longer. My intension was to let the Collection stay, and to watch them from time to time. And my question is; should I Export them or something to make them stored? Or have I missed something on the importing operation maybe? In the filmstrip I can see that the photos are present when i thatch them with the cursor. Please help me. I have got plenty of video among different Collections.