As I wrote it in another discussion forum, I wonder if the FS4000US is properly shielded against electro-magnetic influences from external devices but also from its internal electrical power and electronics.
This could explain the quite cheap price and why it weights only 2.3 kg against 3 kg for the Coolscan IV.
I was near to buy a FS4000 but I'm glad that I choose the safest solution with the Nikon which is an exceptionnal scanner for its price range.
I'm very sorry for those who have problems with the Canon and I hope they will find a way to get their money back.
All this disappointment I can read throughout many web forums remembers me the bad - but short - experience I've had with the Canon 2700F.