Sorry for my very unusable bug report ;) Well, it was my very first play attempt, and in a very early stage in the game, i had two or three pawns and one Knight placed on the board with a production of 14 and no more pieces unlocked yet. But i do not remember wich popup it was, sorry, but i think it had just text in it. I restarted the game now, but everything went fine. Maybe it wasn´t a bug in the game but a hickup from unity :)