Well, god knows what was causing the issue, but I've reached the end of my wick! Some digging and a visit to the Genius bar has revealed that it's definitely a drive issue - whether physical or software I don't know.
Anyway, I've bought DiskWarrior, and that's chuntering away now, in the hope that I can get hold of my files from that physical drive (I've backed up the second Physical Drive already). DiskWarrior seems pretty good!
Anyway, I've bought DiskWarrior, and that's chuntering away now, in the hope that I can get hold of my files from that physical drive (I've backed up the second Physical Drive already). DiskWarrior seems pretty good!