I have a 3tb usb 3.0 wd my book drive formatted in ntfs. I have 2 macs: old imac (first alumium ones on 10.6.8) and a 15 inch mpb:r (first gen of the retinas). There are one or two folders that on the imac appear empty but on the mpb you can see the contents. Whats interesting is that i have plex on the imac and it can see the contents (it locates, ids, plays, and streams the movies on the external drive). I didn't see any extra hidden files when I tried to show hidden files. Any thoughts?