I think I may have solved my own problem.
I had several (6 or 8) files in the Notepad++ editor. Some of the files had been open inside the editor for several weeks.
I closed all of the files, uninstalled Notepad++, then did a clean installation. It seems to be working okay now.
Evidently, leaving open files in Notepad++ for weeks caused something to get clogged up.
One of the mods can mark this thread resolved if they like.