As far as I know it's a relatively new bug. It came with quite recent update to the app. I'm also having the problem and waiting for solution.
The issue has been resolved with the newest update (@07.02.2014).
As the dev wrote:
You must either clear data of the app or uninstall and reinstall it
You won't lose any saved game files.
Last edited by Deathmehr; 7th February 2014 at 07:50 AM.
Reason: Problem solved