I have recently changed from adMob 6.4.1
to Google Play Services rev 15
and have just received notice of a new crash report that I do not understan
This issue was introduced with the latest release of the Google Play Services (v4.3) on the android devices. Google is aware about it and it will be fixed in a future version (not the next one...)
https://groups.google.com/forum/#!topic/google-admob-ads-sdk/sePctoDJbRg%5B101-125-false%5D
I'm not going to claim this is the answer, because I also stopped (completely) and re-started Android Studio after I installed it, and THAT might be the real solution, but Ads were running fine on the emulator and a USB-attached 7" tablet, then I started getting this error. Checking my SDK packages, I noted the Google Web Driver was not installed (this had not been an issue previously) - all other components were (except the USB driver, which is not needed on a Mac). I installed this component, stopped (completely) and re-started Android Studio and the ads started running without error again. It's something to try, anyway.