Nikon D40x Metering Problem

I assume this is no longer under warranty.
This more likely to be a case of not pointing the camera correctly when pressing the release if for example you press the release firmly and dip the camera down in so doing it will register a shadow the camera moves up on exposure and you get a burned image.
Try various experiments in the mode see what happens.
As regards a repair it is likely the cost would be as much as or more then a new replacement
Contact the Nikon customer support