1) With ~ 9 secs left in H1, skins have ball at Boys 3 with no timeouts. What do you do? You throw one pass into the end zone and kick the FG if the pass is incomplete. (Fassel would have Kerry Collins throw the ball into parking lot D4 to make sure he did not lose the FG, but that is another story for another day.) Todd Collins throws the ball into the flat, and by some miracle the RB cannot make the catch because the ball is off target, or else they lose the 3 pts because there are 3 Cowboys defenders ready to make the tackle well before the goal line. This is Gibbs's mistake, period. See Andy Reid if you need clarification on why.
2) With the FG made on the next play, there is 0:01 left on the clock. Mistake #2 comes to the skins because they squib the ball but are boner offside. Wade Phillips makes a great call and figures out that instead of rekicking, he can accept the penalty, tack it on at the end of the play and get one more play at 0:00 because of the penalty.
3) Now it is Dallas's turn to play genius. You have the ball at the Skins 35 with 1 play, what do you do? KICK THE FG! Unless the Skins made a trade with the Bears a few hours earlier, they do not have Devin Hester back there, so there is zero risk, and within the kicker's range. Instead, they run a hail Mary play, Romo gets sacked, and winces off the field in pain, when he was prob done for the next two weeks anyway after halftime.