I have a 2011 Macbook Pro 13" 1278 i7 model. It supports 16GB of memory. The odd thing is, if I put in 2 8GB sticks(correct type), it just does the 3 beep sequence(memory error). Although if I put the sticks in 1 at a time(either slot), it boots up just fine. I've tried using 3 different sets of 16gb memory(all known good), and the same thing happens with each set. Has anyone else experienced this issue/know how to fix it?