Hi! I'm hoping it's just my system - I'm on a Windows PC (i7, 64 bit OS, 8GB Ram). Basically what happened was that the game slowed down a bit, I think, similar to what you described but not for a long time, then it just closed. I was a little wary about reporting it because it might just be my machine and compatibility issues. But I messaged anyway just in case the info might help you.
I finished playing btw, and it was awesome. :)