Windows 10 desktop shortcut keys only work when a Windows folder is open

I've assigned shortcut keys to numerous application shortcuts (right click the shortcut > Properties > Shortcut tab > Shortcut key). I've been using these shortcut keys for years with no problems, but this morning they stopped working normally.

When I press they shortcut key I see a very brief change in the cursor's state, then nothing launches. However, they do work in two situations:

1. If any Windows folder is open




2. Very weirdly—if Firefox is running; I've found no other program that enables the shortcut keys in this way

Other relevant details:

• Most of the shortcuts are in C:\ProgramData\Microsoft\Windows\Start Menu\Programs




• Shortcuts directly on the desktop have the same problem




• All shortcut keys are of the form form Shift-Ctrl-Alt-(key)




• DISM.exe and sfc /scannow reported problems but fixed them, and now they report all is clear




• Multiple malware scanners say all is well




• Possibly related: when I booted up this morning, my desktop shortcuts—which are normally grouped by topic—were all clustered together in the standard desktop "align to grid" configuration, even though "align to grid" wasn't enabled

Any idea what's gone wrong and how to fix it?

I'm wondering whether this could be a problem introduced by a Microsoft OS update. Windows Update History says the following were applied yesterday (Patch Tuesday 9/11/2018):

Answer

This problem has resolved. The cause was either the 9/2018 Windows Update or—more likely—nVidia's driver.

This morning, the October 2018 Windows Update finally became available for me to install (Windows 10, version 1809). As soon as I installed it, my third monitor stopped being recognized. At that point, shortcut keys were still working in the problematic way described in the question.

In troubleshooting the monitor problem, I deinstalled my nVidia driver and reinstalled the latest version. Once I finally got all of my monitors working again, shortcut keys were working consistently.

So either:

1. the fix was in the October 2018 Windows Update, and for some reason
   there was a delay before it took effect; or


2. more likely, since the problem resolved after re-installing nVidia's driver, the problem
   was somehow caused by that software