Angry Birds Evolution needs access to the file system to finish the game's installation. As the game is quite large, it needs to download and install additional files to run.
If you are having trouble launching AB Evolution, please ensure you have allowed all Android permissions requested by the game.
If you do not grant the game access, it will not be able download all needed files and cannot load. If you have denied this permission by clicking "Don't ask me again", you have to manually allow the permission from your device settings to be able to play the game. You can do this by going to:
Settings -> Applications -> Application Manager -> Angry Birds Evolution -> Permissions, and tapping the button next to "Storage" so that it changes its color to blue.