"because it was not writable".
Do you think this might be a clue?
Check the folder that you have in the "Destination" panel of the Import dialog. Know what folder exactly you are trying to copy your files into (or the options for a folder that Lr is trying to create for your).
If the Destination and folder is set correctly, then exit Lightroom and check the Read/Write permissions for the Destination location.
Do you have full Read/Write permissions for the Hard-drive, the parent folders, and any sub-folders, that are in the destination?
Thank you! You solved my problem :-)
Normally this type of error message is a permissions issue. In addition to checking the permissions of the destination drive and folder tree, you may need to do a Disk - Repair Permissions on that drive.
Also, you can refer the below discussion related to the same issue.