I can understand how small errors may go undetected, but surely you have to be pretty switched off to miss 100 tonnes (100,000 kg or 220,000 lb), a Vr 33kt lower than expected......
It is a stinker isn't it?
The point here is that the operating pilots were relatively new to type, yet had 1000's of hours on the A340 which did see such TOW figures regularly. It is a known fact that during times of stress (centre fuel tank error), people revert to their original or predominant training, experience and understanding. It is also concievable that having spotted one mistake, they became slightly oblivious to spotting the other.
transposition errors is a subject that was well covered in 'The Naked Pilot'. Well worth a read for those that find it impossible for highly trained professionals to make seemingly blatant mistakes.