It has happened to me twice since I joined yesterday, both on occasions when I play 2~3 hours into the game. Opening the ESC menu caused the game to non-responsive. Background music stuck. I had to kill process to quit.
On the first occasion, the disk usage was 100% for a long time and I had to reboot. Seems like a memory leak issue.
My OS is Windows 8.1, 8GB memory, Core i7.
Play the game for 2~3 hours. Reaching cycle 40 might be needed. Press ESC.