Thanks, everybody, for the suggestions.  I had tried all those, but thought I'd better try again. Nothing.  Finally, I began removing objects from the render and discovered the culprit.  A three-torus metablob was causing it all.  The material I had used seemed to be causing the trouble. I simply changed the material and...voila....  it worked.  Again, thanks for your suggestions.  I'll post the render later this afternoon. 
Cheers,
mcw1917  (pw2)