Audio problem: Just after the lion takes the deer Neville was hunting at the beginning of the movie, his watch alarm goes off to signal that it's getting dark. The watch alarm in the movie is a "beep-boop" two tone. As the owner of both watches Neville is wearing, I know that the watch we get a closeup of, a Swiss Army Sportech 4000, has a single (once per second) alarm beep and the watch on his other arm, a Hamilton Khaki X-wind, does not have an alarm.
Audio problem: Aside from the beginning of the movie, the generators Robert has going put out a lot of noise that we do not hear during any of the other home scenes. This would make sense for the night shots as they would be off as to not attract anyone, but nothing is heard during any other daytime scene.