With Mexico trailing, USA midfielder John O'Brien clearly handles the ball in his own penalty area.
But despite furious appeals from Mexico's players, none of the officials spot the offence.
Mexico coach Javier Aguirre later said the error cost his team victory.
How bad? Forgiveable, but only just.
South Korea 2-1 Italy
Referee: Byron Moreno
Totti is sent off for diving
With the match in extra-time, Italian golden boy Francesco Totti goes down in the South Korean penalty box after a challenge from Song Chong-Gug.
His appeals for a penalty are not only turned down but referee Byron Moreno awards Totti a second yellow card for diving, reducing Italy to 10 men.
How bad? Pre-determined and provocative.
Tommasi's winner doesn't stand
Damiano Tommasi latches on to a superbly angled through ball and slips the ball home for a golden goal winner.
But the linesman incorrectly flags for off-side.
Italy eventually lose on the golden goal and riots break out back home.
How bad? Just plain wrong.
Brazil 2-0 Belgium
Referee: Peter Prendergast
Wilmots goal wiped
Belgium striker Marc Wilmots appears to have given his team the lead after 36 minutes with a superb header.
It is no less than Belgium deserve after an impressive opening 30 minutes.