MCE error when playing a game

Did something update recently? Yesterday I got a MCE error and it caused my whole PC to reboot. I was playing Call Of Duty BO3 Zombies for a few days and it was running flawlessly but yesterday I kept getting this error. I updated the BIOS but that didn't seem to solve my issue. Maybe it's a GPU OC from LACT? It has been running fine with these settings for months now, though.