This means that the destination directory, where the files are to be copied to, does not have WRITE permissions. Change your permissions.
I am having the same problem. 5D III, importing from CF card. The files obviously can be read since it creates thumbs in the selection screen. The destination is also writable (verified by creating files there). Quite strange. Works if I copy the CR2's to the directory and add them to the library in place, but this is not really a solution.
I've solved this problem with my Macbook pro. Earlier I've tried importing photos directly into the Picture folder in OS X by defining it as my destination which was not possible, the solution however is by creating a separate folder as destination within the Pictures folder in OS X. Now photos are being imported with no more error messages shown. Thanks all for your inputs.
How and where to change the write permission please.
Go to your favorite search engine
change permissions Mac
change permissions Windows