IndexedTriangleStripArray + NormalsGenerator (lighting problems)

Short vsn:

I can't get my lighting to "turn on" WRT to my IndexedTriangleStripArray 
(a "mesh" style terrain) and NormalsGenerator.

Code snippet:

   IndexedTriangleStripArray terrain =
      new IndexedTriangleStripArray (vCount,
         IndexedTriangleStripArray.COORDINATES,
         iCount,
         siCounts
         );
   // Set up coordinates
      [snip]
   // set up indecies
      [snip]

   GeometryInfo gi = new GeometryInfo (terrain);
   NormalGenerator ng = new NormalGenerator();
   ng.generateNormals (gi);

   gi.recomputeIndices();

I've verified that lighting is on by placing a few spheres around the 
terrain, and they light correctly.  In addition, the terrain displays 
correctly and, in fact, even textures nicely (different bit of code.)

Btw, for lighting-testing, I'm turning off textures, as that seems to 
interfere with lighting on my test-spheres.  (Different question :)

Any hints?

Thanks!

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