Possibly Virgin and Air Atlanta could be having a problem with the leasing of the 747-300 that normally operates the flight. Maybe that particular aircraft is one of the 3 747-300s earmarked to go to Iberia and Virgin was left without an aircraft until another leased in 747 arrived? I do know that Virgin is currently over-stretching their fleet and there are really no backup aircraft to speak of. Those B747-200/400s and A340-300s are really working hard!
"History does not long entrust the care of freedom to the weak or timid." D. Eisenhower