I had the same issue this morning. It happened 3 times (usually within the first 2 - 3 minutes of game play), and in order to get rid of it I had to exit the game completely and then re-launch it. I did find a solution (I am hoping). From what I have read, it is a tutorial bug that causes an infinite loop in replaying the turning of the tutorial page (or exiting out of the message). I went into options and disabled the tutorial hints and haven't had an issue at all since I did that (I played for an hour or so without it happening again).
It is a bug that needs to be fixed, but if you can live without a tutorial, then you should be ok for the time being.
