Continuity mistake: When The Rock first enters the scientist's room, the scientist explains to the child about his magic powder. This is on a device that's slowly turning and sifting off a little of the powder at a time, yet during one cut away and back, a lot more powder seems to have disappeared off the mechanism than it would have pushed off itself.
Continuity mistake: In the scene where Cassandra and Mathayus get out of the well after falling through the tub. When they are showing Mathayus from the back of his head his hair looks wet all over but when they show his face, the hair on his head looks dry while the long parts of the hair is still wet. His face has also been dried off when last seen.
Audio problem: When Mathayus and his friends are attacking Memnon's palace, there is a scene where Memnon's general rides at Balthazar on a horse, but then falls off. Balthazar holds a spear at his neck. The shot then changes so we can't see the general and he stabs him and he screams loudly. But if the spear went through his neck (as it should have, as it didn't move anywhere but down) he should not have been able to scream.
Factual error: During Memnon's training session, at least one of his opponents uses a Japanese training sword known as a shinai. You can see this most clearly after the fight, when one of the weapons lying on the ground comes into view. Not only did the Egyptians and Japanese not have any contact with each other at this time, but this particular training weapon had not yet been invented.
Continuity mistake: When Balthazar knocks Matathyus down, Matathyus falls face down and his hair gets covered with white bits of dust (sand or whatever). A brief second later, when he stands up, his hair is clean and shinny, but he hasn't had time to clean it, or even made a single move to take the dust away.