In hunting around the Web, I'm noticing a few other people reporting the same problem at about the same time. This could be just a coincidence; WD hard drives supposedly have a high failure rate, lately. But, 2 other common oddities take place, too:
1) The hard drives are almost full when they fail. Someone suggested to one victim that his drive wrote past the 2.2 TB boundary and the SATA controller wrapped around.
2) Leap second was June 30/July 1, and several computer systems around the world crashed when they did not handle it correctly.
I cannot find a good correlation between the drive failure and the leap second; these failures take place before the leap second does. It just seems odd that so many would happen in the middle or end of June.
Other problems that cropped on my computer about the same time:
3) I also can no longer play Flash in Firefox.
4) Microsoft Word 2003 often stops responding for a few minutes, beginning immediately after the program loads.
I am looking for any information that might relate to this issue.
I believe the reason that some file recovery software could access my 3 TB HDD, but others could not, is that a lot of file recovery software cannot access GPT partitions (they are stuck in the MBR world).