However, beware using this new version. Three readers (Stephen Giles, Rohan Samahon and Erik Carlson) all reported the same problem (and solution): When they updated their hard drive with Drive Setup 1.2.4, their hard drive would no longer mount. Instead, the blinking question mark appeared at startup. Apparently, the new driver had not been installed successfully, even though Drive Setup had reported no problem. (The reason for this is unclear right now but may be due to an increase in size of the new driver and not enough room to install it; similar problems have been noted before with third party drivers.)
In any case, all readers hit upon the same solution to resurrect their drives. They were able to "update" the problem driver with version 7.3.2 (or later) of Apple HD SC Setup (apparently simply using an older version of Drive Setup at this point did not work for them - although another reader did succeed in doing this). Now the drive mounted okay. From there, they were able to "update" the driver again back to the pre-1.2.4 version of Drive Setup that they had been using.
Several other readers have also already reported this problem. It must be a common one!
Also note: reformatting with 1.2.4 should work, even if updating does not.