Continuity mistake: During the scene where Dwight is handing out the goggles, and right before the part where Brenda asks about the walkie-talkies, if you look behind Dwight, you will see that there is one more pair of goggles in the cabinet. After Brenda asks the question, the cabinet is empty.
Continuity mistake: At the end of the film, when Dwight gets pulled into the room and sits down in a chair beside Ray and Buddy, Ray's shirt is orange. Then when Dwight says, "I can't feel my legs," it cuts back, but Ray's shirt is yellow. It alternates throughout this scene between orange and yellow.
Revealing mistake: When the couple split the pole, they get hit by a bus. As the shot cuts to a wide shot, and if you pause in the right place, you can see the couple have been replaced by dummies, just before the bus hits them. [This isn't a "mistake" -- this is just dissecting a movie, frame by frame, until you can spot the special effects.]
Continuity mistake: When Dwight is handing everybody goggles, cup walkie talkies etc., the red numbers on the machine nearby keep changing in most shots. You can clearly see "02.38.58" and it is counting down. Then in the next shot it is "02.39.48" and is counting up. Then it is "02.17.00" etc.
Continuity mistake: In the scene after the main female characters portray Charlie's Angels, they go back to where the guy in the wheelchair has set up a pad that Cindy has to lure the ghost into, from one shot to the next (when Cindy goes to lure the ghost) Cindy's lipstick colour changes instantly from red to beige although her clothes stay the same.