Nikon SLR lens autofocus not working properly?

I'm having trouble with my lens on my D40, it used to work ok but now if I change lenses or turn of the camera my 55-200 AF shows out and won't autofocus. I have to jiggle it or take it on and off repeatedly to get it to work. Any suggestions on what the problem may be? Or how much it would cost to repair?

First call Nikon, this may be under warranty.

Before you call Nikon I'd suggest you pull the lens and very gently clean the contacts you find on both lens and camera body. This is the way the camera and lens talk. Dirt… No talk. Try that first.
Also check the switch on the side of the lens to make sure it's firmly seated into auto focus.