Do you run Skype, Kaspersky Antivrus, Camtasia, SnagIt, CamStudio, or something similar (that has to do with screen capturing or screen sharing, for example)? These applications are known to interfere with drag&drop.

And what version of GIMP is this?

I am running GIMP 2.8.18

I do have Skype and OBS installed, but neither are running while I am using GIMP. They didn't interfere with GIMP's drag and drop while I had Windows 7, as I used OBS to make a tutorial video in GIMP for a friend.

If the problem could be screen-sharing related, could a dual-monitor set-up or other display setting interfere in some way?

No idea. The applications I mentioned were findings by affected users, so we are basically relying on you to find the issue on your system. If you do, please tell us what was causing it.

Found anything yet?

As mentioned in the last few comments in http://www.strokesplus.com/forum/topic/750/open-enable-s-if-this-application-is-stopped, any application which makes use a an invisible full-screen window may cause this.

I have some software installed (Skype, OBS) that are mentioned in that forum post and in previous comments.

When GIMP is the only program running, the issue persists. I uninstalled Skype and OBS and the issue persisted. I set my display to only utilize one monitor while the programs were uninstalled and the issue persisted. I also disabled Windows Defender and Avast Antivirus and the issue persisted.

If the problem is coming from another application, it would have to be one of the background applications that run as part of the OS. Task Manager lists many such applications and services running as soon as my computer starts, but they all have technical names and I don't want to risk turning off a service that causes my computer to crash.

If I get you a list of these background apps, would that help in any way?

On a whim, I restarted my computer in Safe Mode. The issue did not appear while in safe mode.

So it is something that's running.

When you got your computer, did you wipe it and reinstall Windows 10 from a clean image (e.g. one obtained directly from Microsoft), or did you keep whatever the manufacturer of the system had installed?

I bought the computer from Best Buy with Windows 7 back in 2008. I upgraded to Windows 10 in 2015 when Microsoft did their promotion for free copies through the Windows Update system. The copy of Windows 10 was obtained directly from Microsoft, the computer was never wiped, and it simply installed Windows 10 over top of Windows 7.

Coincidentally this just started happening to me within the last few days: all of a sudden no drag & drop for layer ordering or layers between windows.  I haven't had any changes to Windows version (W10) or any changes to Gimp version (2.8.18).

And yeah the culprit for me ended up being a recent update to Nvidia Geforce Experience screen capture software.  Disabling the Desktop Screen Capture under Privacy Settings (which I've had on and had been using fine before) fixed it.

I have an NVidia GeForce graphics card, but do not have the Geforce Experience program. I searched through Task Manager for all background tasks related to NVidia and force-stopped them (just in case). This did not fix the issue.

I also checked for any tasks related to screen capture software (OBS, Skype, Steam) and force-stopped those. This did not fix the issue.

Hypothetically, if one of the tasks I stopped was causing a problem would force stopping it immediately allow Gimp to function properly? Would I need to restart Gimp? Or restart my computer?

Hmm, not sure about force stopping tasks but I -did- have to restart my computer after disabling the desktop capture stuff through Experience before d&d started working properly again.  Reloading Gimp had no effect until the computer was restarted.  Sorry, hope any of this helps.

Consolidating this class of bugs into the one where we identified the trigger.

*** This bug has been marked as a duplicate of bug 780979 ***