[Nick]

The failures began last night: About 75% of the way through, SD! would simply stall. After an hour of waiting, I'd then press the "stop" button, get the usual "SD! ain't done yet...you sure you want to stop?" message. I'd say "yes," and that would be it....except that although it stopped, it remained open, and I had to either quit from within SD! itself, or force quit.

The only thing that caught my attention as being a bit "odd" was that although the SD! window indicates the usual:

---
What's going to happen?

Pressing "Copy Now" will use "Backup - all files" to copy Nick's HD to Nick's HD Clone ..."
----

the top portion indicates:

---
Copy Nick's HD to Nick's HD Clone 1
---

whereas in the past, I'm certain it simply said:

---
Copy Nick's HD to Nick's HD Clone
---

When I checked with DU, I found that the volume indeed had what I believe is a new "mount point":

Mount Point : /Volumes/Nick's HD Clone 1

(I don't know whether this apparent mount point change is significant or meaningful, but I though it worth mentioning.)