I spent several hours yesterday night trying to fix model errors that didn't show up in Meshlab or Blender, but that didn't go through Shapeways (mostly inverted normals error). I thought it might be useful to know how I fixed it (I was using ViaCAD Pro). It seemed to be a problem with overlapping solids.
In the end I did a "merge solids" (or "add solids") for all connected parts, and then it passed all checks. You can see the final model here