Ah! Problem solved. Under Gallery -> Options -> Gallery Settings , Show First should be set to Thumbnails, NOT Slideshow.
BTW, I'm using this for an architecture firm which requires text descriptions for the body and excerpt, so I wanted to make it easier for the user to embed the gallery without having to know HTML. Solution was to tweak the single post template using the do_shortcode function, pulling the gallery ID from a custom field attached to the post.
Makes it easy for the user to create a gallery and then attach it to a post.
Thanks for the elegant solution to the mini-thumbs under a big image!
Best - Holling