I'm encountering a problem importing photos. My first attempt was using a card reader and subsequent efforts I've connected via the camera. Most of the time the import bar starts at half but then doesn't move.Twice it seemed to proceed with the import, showed thumbnails and then said it couldn't continue (I didn't write down the message and it hasn't shown again). However most attempts the import seems to start, the progress bar seems to start at half, then it stops (forever), and no previews show. I then stop the import, eject the source, and close LightRoom. However I need to force quit before I can re-open LR. I've followed several suggestions including upgrading to 5.6. I already have upgraded my Mac to the newest version 10.10. I tried moving/deleting the preferences folder and nothing makes a difference. I also have LR 5.6 on my laptop so I tried importing on that and had no problem. Any suggestions?