Chu Chu,
In this event the erroneous weight was entered in the Electronic Flight Bag not in the Flight Management and Guidance System.
In that case my lowly 737 FMC would have alerted me to the issue. It shows computed QRH values for V1/Vr/V2, if the there is a big difference, especially to the negative, i certainly would question my own performance calculation. Only if i put in the wrong ZFM in both the EFB and FMC i would have a real problem.