Interior Courtesy Lights problem

I am having a problem with the interior 'courtesy' lights (i.e. the lights that come on when you open/close the doors). They are not turning off when the door is closed. I've had the truck for about 2 months and have had them work off and on, but have to keep the switch in the permanent off position because i'm not sure if they will go off or not. Its kinda crappy getting in at night and not being able to see anything - anyone know what could be causing this? Thought maybe some suggestions before i go to the dealer.