I recently installed an upgrade to Lightroom. Since then I have not been able to import photos to the library. I get the message, "Could not copy a file to the destination folder because it is not writable." This happens to both JPG and raw photos and ones from a Nikon and Canon camera.
This means that the folder you are trying to copy the photos into is not writeable, and you have to use your operating system to change the permissions on that folder to WRITE permission. Or change the folder to some folder that is writeable.