However, the newest Google Play library includes ads and my guess would be that you are including both Admob and Google Play Services which apparently contain the same classes. In that case you should migrate your code to use the Google Play Service ads and remove the admob jar from your project.
とありまして、つまりGoogle PlayにAdmobが入ったので、Google Play Libraryを読み込んでいると、この衝突が起こるのではということでした。
ということは、