It could be that the Google Play store connection cache itself corrupted, in this case, you may try this: Go to settings > Applications > Manage Applications > Select ALL > Select Google Play Store> Select Clear Data. Press the Back button, go back to ALL then scroll down > Select Market Updater > Select Clear data. Press the Back button again then go back to ALL then select Google Services Framework > Then select Clear Data again. Then turn off your phone, take the battery out then put it back and turn it on again. Now try to download the app again.