The only thing I can thing I can think of is, did you get the separate (on a d2, not sure on a d1) ground wire hooked back up to the metal plate behind the light? or possible, the grounding lug (on the light itself) was damaged on re-installation.
The ground lug on the light is held by a nut, that attaches to a metal plate behind the head liner. a ground wire attaches to the plate. if this makes any sense.