title: error "app not installed" when installing apk
body: <p>I have an app in development that I am trying to copy to a tablet to test. 
  The app will run in the emulator and will run on the tablet when connected by USB.  This is my first Android app so forgive me for the newbie question.</p>
  
  <p>My USB cable is temperamental and until I get a new one I am copying the apk to the tablet via dropbox.  I also tried emailing myself the apk.  All result in the same issue.</p>
  
  <p>When I try to install the app I get the error "app not installed".  But I have uninstalled previous versions and made sure it does not show in the app drawer.  I even looked through the app drawer and made sure there were no unrecognized apps.</p>
  
  <p>If I change the build type to debug and generate an app-debug.apk that will install and run fine on the tablet.</p>
  
  <p>But If I change the build type to release and try to install the app-release.apk I get that error.</p>
  
  <p>I have also tried this on another tablet and my phone to see what happens and have exactly the same issue.</p>
  
  <p>Any help is greatly appreciated.
  Thanks</p>