[dnanian]

Assuming you did a "Backup - all files" with "Erase, then copy" or "Smart Update", I'd suggest booting to Option-boot with the drive disconnected. Once you're at the drive selection screen, and the watch has turned to an arrow, plug in the LaCie.

Wait for it to spin up, then press the Refresh button. The drive should show -- select it and press the "-->" button to boot.

Let me know if that works.