I recently got two Seagate 'XTreme' 1.5 TB drives as well, eSATA, USB & Firewire 400 all in one case. Fab, I thought, I can use them at full speed on the Mac Pro, and firewire or USB from the MacBook. Then within a fortnight they'd both started making the same ominous clicking noise and farting I/O errors at the console.
So that's XTreme as in "XTremely irritating", then.
And back they go.