I have a small office with the 'standard' florescent lights in ceiling. (4 tube, fat 4' tubes, with 2 ballasts) - In some rooms, I flip switch and no lights come on. Sometimes, if I flip the switch multiple times, it turns on; sometimes not. If I leave in 'on' position (up), they sometimes turn on in 10 to 20 minutes by themselves. In a room with 4 sets of lights, one or 2 sets turn on, and maybe in 10, 20 minutes later, the other 1 or 2 sets turn on. Could this be a corrosion thing? I replaced one switch - but no change. Help!!!