I have a MacBook Pro (mid 2010) with Yosemite, Lightroom CC and Canon 70D. I have three almost full 64 gb SD cards and usually I have no problems with the import process, but now everything (!!!) is tricky... I will list up the different problems, and hope that some of you can help me:
What can I do?
With regards and thank you in advance,
If you use Finder to Copy the image to that Prove folder on the external drive does Finder (OS X) Freeze? If it does then you have either a problem with that SD card, a problem with the external drive or a problem with your Mac. Finder should not freeze during the copying of files from on drive (hard drive or memory card) to another drive whether they are internal or external.
I suspect that memory card is going bad or has some corrupted files on it that can't be read. Just like physical hard drives you shouldn't fill up a SD memory card all the way. Always leave at least 10%, and better 15-20%, free space on all drives of any type.
Try using Finder again only this time only select a few images at a time to copy. Like 20-30 files at a time. If it still freezes with some reduce that number to just a few to sort out the files that are causing the freezes. That mean some will need to be copied one by one so you can record and omit the ones that are corrupted.