I have a 2012 Macbook Pro 13" that came with 4GB ram (2GB x 2) I bought a Corsair 16GB Kit (2 x 8GB) 1600mhz After installing, the mac locks up after a few minutes of use, horizontal lines on the screen. I've used the mac hardware tester and the same thing happens, just the horizontal lines are thicker. So for testing I used ever combination of the 4 modules I know have, and the only one that duplicates the problem is when the 2 8GB modules are installed. I've tried, 8GB + 2GB, swapping out trying each 8GB module, no problems. Tried each of the 8GB modules by them selves and no problem. Whenever the two 8GB are installed I get the crashes, it even crashes the hardware tester.