Would suggest you to go to Lightroom Preferences > Performance > uncheck "use graphics processor" > relaunch Lightroom and then, try to import again.
If this does not help, copy the images from your Canon EOS 5D Mark III to your hard drive through Finder and then, try to import in Lightroom to test if that works.
Hi. Thank you very much for a fast and correct ansir - I uncheked "use graphic processor"
But why is this problem coming out of the blue. And a pity if I can't use my graphic processor. I assume that Lightroom will slow down now?
It would not slow down the program. GPU is required if you create HDR and Panorama in Lightroom.
You need to make sure your graphics card is supported and the drivers are upto date if you want to use it : Adobe Lightroom GPU Troubleshooting and FAQ
...First I helped, as mentioned above, but I soon realized that there was still some pictures with same problem.
If I reliance again the problem is again the same now with nearly all photos.
If I copy within finder to hard disk and then import from hard disk to Lightroom there is no problem?
So I am still confused - why am I suddenly having this problem?
If you are able to import from hard drive, then it could be related to permissions of the source location.
Make sure that the device from which you import has full read and write permissions to be accessed.
This can be done via finder.
I had Windows PCs for years and never had any issue with this on any of the versions of Lightroom I used (LR 4, LR5, and LR CC)
Just recently switched to a Mac computer and started having this issue. It isn't for all of the files, just about half of them. I tried to unclick the "use graphics processor" option, but that didn't help. It just changed it to were some of the files that I weren't able to preview I can see now, but others that I could preview now I can't see.
Which version of Lightroom do you have on your Mac machine?
Is it updated?
Does this happens for specific camera files?
Could you please share a screenshot explaining the exact issue?