Well, I'll be damned. D-Link Australia finally accepted my request to send the thing back to them.
In the mean time, though, I have two drives that are still in the DNS-345 that I need to get working in my Linux machine. I previously pulled one drive out (from Volume_1, as detailed in my OP), chown'd and chmod'd it in Linux, and then all was fine.
However, to chown and chmod it, you have to be able to at least access the partition. So I did this again for one of the other drives, but am now finding that the partition isn't visible (and, hence, I can't chmod and chown the files).
Any ideas? Thanks in advance.