With a Linux host, sometimes for some reason, Windows drag and drop randomly stops working, even though the drag and drop is enabled in the VM, and even though the guest-utils are still installed and running in the VM.
I find this usually fixes it:
Reinstall or update the guest-utils driver within Windows and restart. Usually/hopefully that fixes it.
After that stop your VM and start it again and hopefully drag and drop works without aborting the........