Plot hole: In the shot where two of the pirates find Jack Sparrow in the prison, you see the moon shine out over Port Royal and the pirate's hand around Jack's neck is skeletal. While this is happening we know that Elizabeth is being led onto the Black Pearl by two pirates. If the pirate in the prison turns skeletal, why don't the pirates with Elizabeth turn skeletal? It's clear that they don't as Elizabeth only discovers the curse later on aboard the Black Pearl.
Plot hole: Elizabeth goes to drop the medallion over the side of the Pearl. Barbossa and the crew gasp and take a step forward revealing they want/need the medallion thus giving Elizabeth the upper hand in the negotiations. Why not let the medallion drop into the water below the Pearl and simply "take a walk" to get the medallion off the ocean floor? The crew can walk under water as shown later in the film so this shouldn't be an issue. (00:38:15)
Factual error: The scriptwriters revealed that they placed the story in a thirty-year environment set loosely between 1720 and 1750. Port Royal was destroyed by an earthquake on 7 June 1692, which had an accompanying tsunami. An initial attempt at rebuilding was again destroyed in 1703 by fire. Subsequent rebuilding was hampered by several hurricanes in the first half of the 18th century. I don't remember if the movie was set in a big, undestroyed Port Royal. However there was also set a huge fortress in Port Royal, which is definitely a factual error.