Whatever hairgel they used in the matrix was not good enough....
Scene: Trinity is talking to Neo after he's been shot by Agent Smith in room 303.
Trinity is whispering to Neo and her slick hair parts and starts falling off to her face.
Scene cuts to Neo lying in front of her.
Next scene she has not moved, is still talking to Neo, and her hair is neatly back in place but her hands never touched it!
Cut back to Neo.
Then the next scene you see her hair dangling by her face again!