I suspect a bad ground. All the interior electrics share a few grounds throughout the car, and if one ground group gets loose or starts to corrode, it can make some funny things happen.
Try taking a jumper wire and finding a good ground anywhere in the car. Then find something metal under the dash, and ground it. This should give you a decent ground, and if thats the problem, it should fix it.
Try taking a jumper wire and finding a good ground anywhere in the car. Then find something metal under the dash, and ground it. This should give you a decent ground, and if thats the problem, it should fix it.