Firstly, please ensure that the device's memory card is not mounted as an external drive on the computer. Mounting your device as an external disk will leave the game (and probably most of your other apps) unable to run. On older (pre ICS) Android devices, make sure the connection type is set to 'charge only'.
Secondly, please try fully rebooting your device and running the game again.
If neither of the above have met with any success, it's possible that some of the game's data may be