name='icestation2']I recall a movie probably made in the early 80's which is set in a big US city like New York. It features a young guy who is into the whole dungeon and dragons thing, and for some reason he believes he is the Gatemaster or something similar. I can remember him or a group of hippie type people trying to search for something.
Mazes and Monsters with a very young Tom Hanks would fit that description. He starts to lose his sense of reality and confuses the game with real life.
Much of it was filmed in Manhattan. I remember it well. I don't know if that is what you are thinking of.