Nope, it's Boxcryptor or the way it interacts with Windows 10 after the Creators Update, perhaps. Could be unrelated to that update, hard to say the exact timing when this started.
After uninstalling Boxcryptor, restarting, installing the latest version again, and restarting, I can now copy files directly to the Google Drive folder without Windows Explorer crashing--although I suspect that has more to do with the restarts than with anything going on with BC.
But BC still crashes Windows Explorer when attempting to copy files into the BC drive. I can copy files FROM the drive, and I can create new files (Word docs etc.) on the BC drive as well as modify existing ones...just can't copy files to it.