Peter, 

Thanks for those suggestions, which helped a lot.  The first thing I did was change check DX Summit from every 1 minute to every 2.  That seemed to help a little.  Then I got rid of show SNR Filter, Show SNR. and Show SNR Icons.  That helped a whole lot.  What made the big difference was uninstalling HamCap, which wasn't giving good information anyhow.  Now when I see all spots in the Main window, I can  use the scroll bar by holding down the left mouse button for several seconds before attempting to scroll.  Only the scroll button moves, but not the spot list until I release the scroll button.  I think that's normal.  Bandmap scrolling is completely normal, though.  My computer is fast with lots of memory, and this problem only began a couple of weeks ago after working normally for years.  I suppose it's possible that changes in my ESET Security software could have been a big factor.  I think Leo Laporte still recommends it.  As always, your help is much appreciated!   73, Jim W6YA