Possibly a break in the wire, but doesn't seem likely. I'm assuming all the bulbs are still good. I worked with a lady once who had one of my coworkers check her car because none of her exterior lights (headlights, taillights, etc) were not working. He checked all the usual suspects. it turns out all the bulbs had burned out one by one and she hadn't noticed! I'm guessing that is not what happened to you.
the only other thing that comes to mind is the dial on the dash to the left of my steering wheel on my 97. It is used to turn on the interior lights and it also dims the dash lights. Maybe there is some connection with that.
Good luck
