Thanks, guys!! I had synced to the Shared User Account folder. And I think because of permissions, it wasn't working, even after I tried to change ownership (chown) of the prefs file (recursively) and its encompassing folder.
But I set up sync to my new dropbox account, and it worked beautifully. Thanks, Roger, for giving me confidence in the Prefs file, and David, for the info which may be useful later.
Very happy to have Alfred back in my life!!