When you copy and paste songs and playlist in Emplode (and also I assume Jemplode as well) you are not creating new copies of those songs and playlists. You are just creating additional links to the original songs and playlists. Hence, any changes you make to one will appear in the other-- they are the same object. This is by design. If you do not wish this to happen, create new playlists from scratch rather than making copies of them. The FAQ entry is here.