Hi Fluidmosaic,
First off, a 740/Q48 is an outstanding score (it's just shy of the 99th percentile overall), so you can comfortably apply to any Business School with this score. As such, a retest is almost certainly not necessary. You have to remember that Business Schools are looking for strong OVERALL applicants and no GMAT score (not even an 800) will guarantee you anything. Since you have a fantastic score 'locked up' you should concentrate on the other areas of your application(s).
1) What Schools are you planning to apply to?
2) When are you planning to apply?
As an aside, how far did you get into your Official GMAT before you learned that you could not have a calculator with you in the Computer Lab?
GMAT assassins aren't born, they're made,
Rich