Downloaded Chapter 2 on Steam. I get the opening credits right up to the title screen, then it turns black and stays that way. Still playing the music, though.
OSX Mavericks 10.9.5
2.7 GHz Intel Core i5
8GB 1600 MHz DDR3
NVIDIA GeForce GT 640M 512 MB
Never had any problems with Chapter 1, same machine.
I'm switching to Yosemite now and see how it goes.