Due to a change in the way Unity handles AndroidJava classes in version 4.2, some plugin code will now raise exceptions in the editor (used to produce a warning) but work fine once deployed to an Android device.
The fix is simple, wrap each AndroidJava class call in a try…catch block, but until I get round to updating all my plugins I will post a link to the amended files below. The linked files have the try…catch blocks added.
Google Play Game Services
In-App Purchase (Android)