Please list the make and model of your player and I'll move your post to that player's owner's thread. Are you talking about lettering boxing of movies too. Give specific examples of the scenes, titles, previews that your are seeing this on. As it stands we don't have enough information to answer your question.
The movie is 2.35 aspect ratio. I don't remember the previews shown before the feature. If you have a 16x9 TV...you have to have bars on the top and bottom to preserve the proper aspect ratio of the movie on your screen. Is this what you are referring to?