Audio problem: Just as McClane and Farrell are about to leave the Eastern Power Hub, Farrell goes on a long rant and his mouth does not match the words he is saying. Submitted by Joel Amos Gordon

Continuity: When McClane first brings Farrell to the Cyber division, McClane has a cut over his eyebrow that he gets from a fight scene later in the film. [This mistake is pointed out in the DVD audio commentary: this scene was filmed after said fight scene was completed.] Submitted by Cubs Fan

Continuity: In the scene when Bruce Willis is driving the police car up the ramp to blow up the helicopter, the guy jumps out. As he jumps out he has got headphones on, but when he lands on the car they fall off. The next scene it shows him taking them off. Submitted by gonewiththesin

Other: If the natural gas could be rerouted to McClane's position at the national grids control center, there are two major problems. The gas would not self-ignite on it's way there as pictured and secondly, the sheer momentum of that massive amount of gas in those long pipes would cause a massive leak at the endpoint. However, after the first (relatively small considering the total energy in all the gas) explosion everything goes back to normal without one giant amount of gas erupting. Submitted by Andreas Winnberg

Continuity: Near the start of the chase involving the HAZ-MAT van and the semi, John runs into a black Mercedes Benz car, skewing it round to the left of the cab, later on in the chase, he hits exactly the same Mercedes.

Other: Where does the fire in the gas pipes come from? Even though a lot of gas - and thereby pressure - is directed towards the power station, why do they blow up under ground far away from the power station? Submitted by Jacob La Cour

Revealing: When McClane goes into the icy room in the power station, look at the pipe to the side of him: it's in shot a few seconds and you can see that the writing on the pipe is reversed, revealing that in the editing room, the shot was flipped.