Firstly, let me state these are Mac HSF+ Journaled drives NOT NTFS. So *that* is not the issue. This morning I booted up VisualDiffer (great app by the way) to do some copies between harddrives and was shocked to discover that when I tried to copy files I got a permissions error "/Volumes/4 TB WD Backup/Music: You don’t have permission to save the file “Music” in the folder “Audio Vault”." Was obviously confused since this had never happened before. Did a get info on the drive and the permissions read: System: read & write wheel: read & write everyone: read only Un-locked the little lock and set "everyone" to Read&Write and now I can write to the drive just fine in Finder but not in visual differ. This was the same for two completely separate harddrives that I had connected to my system. If I do a get info for the folders inside the drive the permissions are as follows: username: read & write staff: read only everyone: read only These drives have never given me trouble before (in fact one of them is brand new and just had it's data cloned over from another drive that i'm returning to Amazon today). Opening (different) external drives connected on another mac that work just fine (i'd check these on that computer as well but they're finally copying and I have a rather large transfer going that I don't want to interupt) I notice that the permissions are similar to the folder: username: read & write staff: read only everyone: read only Interesting that the drives currently hooked up to THIS mac don't have an entry for the username but only "system". It should perhaps also be noted that both of these drives were hooked up to my Time Capsule (the first drive, the 2TB drive was an expansion drive that got upgraded/replaced with the new 4TB drive). Since I wanted to merge the data I plugged them both into this computer to check everything and this is where my problems began. As i mentioned, setting the flag for "everyone" to read and write allowed me to write to the disks but I'm not sure that's a good idea moving forward, especially since it seems that there should be an entry for my username and not system. Any help would be greatly appreciated. UPDATE: Added wrinkle: one of the drives just gave an I/O error through SMART reporter. This is the older 2TB drive that had been cloned to the newer 4TB drive. Ugh. It's going to be a long night.