I've got a problem where some imported objects are lit from the wrong direction. See center object below. Normals are ok. I assume there's some sort of transform linked to the object, but I can't see how or where to reset it.
Fixed: Face and vertex normals were okay. However, Blender tries to auto generate vertex-per-face normals and get all mixed up. Once you turn this off, all works just fine. Thanks to this post for the solution: How to unify face and vertex normals