Maroney's second vault of 14.300 combined with her initial 15.866 gave her a two-jump average of 15.083. It was good enough for a temporary spot in first place, but allowed the final competitor, Izbasa, a chance.
Maroney was disconsolate after she failed to land on her feet on her second vault. She was expected to win America's first gold in the vault after a breathtaking performance during team competition.
On Tuesday she delivered a remarkable 16.233 that legendary gymnastics coach Bela Karoyli deemed the greatest single vault in the history of the sport.
Maroney appeared on her way with the 15.866, by far the best single jump of the individual competition.
[ Photos: Maroney takes hard fall on second vault ]
Then came the disastrous second vault. While she was rewarded for attempting the difficult Amanar vault, which includes a daring two-and-a-half twists in the backward summersault position and requires incredible speed, power and dexterity, the fall was too much to overcome.
The United States already captured gold in team and all around (Douglas).
Douglas and Ross compete in uneven bars Monday. Douglas and Raisman are in the beam finals on Tuesday and Raisman and Wieber are in the floor exercise final.
Maroney, a 16-year-old out of Laguna Niguel, Calif., had developed into a vaulter for the ages this year, making the silver a difficult consolation prize at this point.
Still, she becomes just the third American to medal in this event, joining Mary Lou Retton (1984) and Annia Hatch (2004), who both captured silver.
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