Factual error: In one scene Alvin is driving over a bridge on the Mississippi. He is going in to Prarie Du Chine but the bridge is in a different town, and he is going from east to west not west to east. The town he is driving into is Lansing, Iowa.
Audio problem: When Alex is appointed head of Netforce, he looks down for a moment and says, "I don't know what to say." And then looks back up. His mouth is in clear view the full shot, yet never moves once during this line and is completely shut. The audio was just dubbed over the footage in post. (00:23:25)
Character mistake: When Amy goes to Virgil's house to apologize, Virgil tells Amy that the tree is exactly 14 steps away. However he then leads her there by taking 17 steps.
Factual error: The story takes place in the Pacific Northwest (Vancouver) in November and December. Washington may be known as the "Evergreen State", but there are still numerous deciduous trees - and deciduous trees have leaves that change color in Autumn (yellow, orange, red) and then shed (fall off), not stay green through December or into the new year.
Factual error: Hornblower's plan is to sail Le Reve south from Gibraltar to give him ample sea room before he heads for England. Generally, the prevailing wind through the Straits is westerly, unless there is a Levanter, yet Le Reve is shown on a port tack when it should be on a broad reach. The fog that comes up would not exist in a gale-force Levanter.
Other mistake: Louella Parsons walks out of a screening of Citizen Kane before it ends, but later tells Hearst that Rosebud was Kane's sled. She shouldn't know that, because the identity of Rosebud is only revealed in the final scene of the movie. And if she disliked the movie enough to walk out on it, it's improbable she went to see it a second time.