simple thing, your mesh is too lowpoly your faking smoothness with normalmaps but your mesh is still as lowpoly as the unsmoothed version would look like, so how should the raytracer cast the shadows, if not based on youir lowpoly mesh
No need to sharpen the edges. Just triangulate the lowpoly before baking and make sure to use that same export for previewing too. The baking lowpoly and preview lowpoly must have to have the same triangulation, otherwise these kinds of errors will show up.
Hello! These are my highpoly and lowpoly versions of a cupboard I did for my modeling class. Critique welcomed :) Highpoly Uploaded with ImageShack.us Lowpoly Thank you, Jessica Dinh