[sylpheed:37347] Mouse problem in Sylpheed with new monitor

[Gene Goldenfeld]

Sylpheed\Win32 (Win 10 Pro). This is a strange one. I've been using a
Dell U2412M 16:10 monitor for years, but today set up a Dell Pro P2425
16:10 in its place and updated the monitor driver and screen settings.
Everything seems fine except for one thing: in Sylpheed, drag and drop
doesn't work and, after opening a folder, it won't close without
considerable delay. And if I finally get it closed, it usually won't
readily reopen. I can use right-click>Move to get emails to a folder,
but if the folder has subfolders, they won't open. If I go to send an
email, sometimes the mouse pointer may take a few moments to show on
Send or doesn't at all until I click in a browser page first and then
come back. Outside of Sylpheed, I did find one website (Dell's) where
the Submit button didn't respond, but that can happen sometimes with
Opera, so I'm not sure about that one. The mouse driver is up to date.

Has anyone come across anything like this before? 

Gene