Phone call by Kuwaiti courier led to bin Laden - Yahoo! News:
"The helicopters lowered into the compound, dropping the SEALs behind the walls. No shots were fired, but shortly after the team hit the ground, one of the helicopters came crashing down and rolled onto its side for reasons the government has yet to explain. None of the SEALs was injured, however, and the mission continued uninterrupted."

My guess is they will have to edit that little sequence out of the forthcoming biopic of the event. Nobody would ever believe it.

UPDATE: According to the New York Times, "One of their helicopters stalled and could not take off. Rather than let it fall into the wrong hands, the commandos moved the women and children to a secure area and blew up the malfunctioning helicopter." This was at the end of the mission rather than the beginning and makes a lot more sense.