Sorry to hear about the inconvenience you are experiencing.

Are you sure your installation is intact? GOG has a Verify/Repair feature that you could try first.

In additional, could you please press Alt+B in the game to send a game state to developers? This will allow them to analyze the issue. In the form displayed by Alt+B, you don't need to specify an e-mail address if you don't want developers to contact you about the issue. The developers can keep you informed here, in this thread as well.