when your lights go off do they (when they are supposed to be on) go completly off or do they dim to the point you can barly see them. if they dim and make other ones go on it always has been a ground problem when i had to deal with the stuff, when you reground the wires make sure you get clean metal, no paint, rust or white powdery stuff. if thats not it than you got a heck of a job on your hands, following the wires is no fun, did it, didn't like it.
most recently i had a problem with my reverse lights going on when i put lights on (not always but when they felt like it) believe it or not it was resedue in the trailer outlet (or whatever you call it, the one on the bumper you plug a trailer into) greenish whitish acidic liqid stuff collected in there and shorted out all three wires, melted one of the metal pieces too. cleaned it out, cloged it with havy amounts of greese, never happened again, but than again you said you disconnected it so that can't be it.
Will work for mods
Current mods--> 31x10.5x15 ProComp MT, 15x8 AR767 rims, K&N, MSD Ignition Coil.