[Stoofa]

The 750GB Seagate mentioned in the other thread is by far the best drive to use in the Samsung boxes - 100% success rate with them at the moment.

Quite why the Samsung box is having these problems is unclear.
The voltage issues appear to have been a red herring.
A friend of mine who works in Sky R&D also couldn't work out why - a recent software upgrade (released for other reasons) may have had the result that the Samsung boxes would be less picky on upgrade discs.
Alas that didn't happen.