It looks there is still an issue with deleting games at the moment.
If you are desperate to stop people playing your game for whatever reason, just do what I did and create a new version for export that just had the main screen but the rest of the game is gone - so it's actually unplayable - and update the online game.
When Tom gives us the new arcade, supposedly we'll be able to delete our games ourselves, which would save a great deal of messing about.