The problem was not so much that there were high spots, but that I was a little uneven on the pressure I applied while sanding. I also use a palm sander to speed the sanding process and I was a little careless in these spots. The bald spots are fairly small and hard to see, but I know from previous experience that these spots will show through the paint if not repaired. There are two to the right in the picture, and one to the left near the edge.
I guess I could seal the spots with some polyurathane for painting pruposes.
John