After fiddling around with it some more I see it's a zoom problem. In
order to change the zoom I have to be 'off' the chart. When I change it,
the chart grows or shrinks, and the scrollbar seems to stay over the same
ROW as it should, but the horizontal placement stays the same relative to
the screen, NOT THE COLUMN. Whatever I change the zoom to, the scroll bar
stays (horizontally) pretty much in the same place (about the middle of
the screen).

If I click on the chart in any of these zoom settings, the scrollbar jumps
to where it should be on the re-sized chart if everything were shrinking
and growing to scale like it should when zoom is changed.

In other words, the horizontal placement of the scrollbar on the chart,
when the chart is not clicked, is always (roughly) like the zoom is 100
percent. When the chart *IS clicked* horizontal placement works with Zoom
as it should.

The bottom line is: if you don't want the scrollbar jumping around when
you click on and off the chart, you have to leave the zoom at 100, or take
the scrollbar off the chart.

....... unless someone else has some other ideas......?