I have been playing around some more with my nexus and discovered the google play store quit working. I get a message 'unfortunately, google play store as stopped'. I tried various things to fix it. finally decided to do a factory reset since I'm basically still trying to learn how to use this thing. That didn't solve the problem, and now I notice I don't even have google play books on my device anymore. hmm..... any idea what I'm doing wrong?