Its a new firmware
Just flashed my (so far problem free) ST3500320AS SD15 to SD1A using the latest firmware. It worked fine. I waited till I saw other people had done it first though! There are plenty of posts in the seagate forums saying it works.
If you bricked your drive using the old SD1A firmware that was taken offline, this new one will bring it back to life, just as long as your BIOS can still see your drive. If your BIOS can't see your drive, you're out of luck.