To trash the prefs. Start by quitting Lightroom 5.
Launch Finder and from the menu bar click Go whilst holding down the Option (alt) key. Then go to Library >> Preferences and clear everything relating to LR5 which usually means deleting the following files:
Then re-launch Lightroom.
Also check the privileges on the main Lightroom folder and Pictures folder or sub-folder you are importing into. Right-click on each and press Cmd+i and in the info dialog ensure read and write permissions are all enabled.
99.999999% of the time this is caused by a permissions problem. Your Username does not have the rights to modify the folder you are trying to copy/move the images into. With OS X this can happen at any time. OS X can change permissions on a folder at the drop of a hat without any warning or reason. A folder you HAD access to can all of a sudden be restricted. So check the permissions on the folder you have select in the destination area.
Thanks! You nailed it, I changed the destination and voilá!