The first time it happened, I was on the interstate and had to hit my brakes rather hard in order to not hit a deer. I was able to quickly get across the road to analyze the problem, but I wasn't able to uncover anything significant. It happened again today as a result of an idiot pulling out in front of me. I hit my brakes, not even in a panic, but hard enough to cause the engine to stall. After doing some research, I have found some likely causes. IAC or Idle Air Control Valve not functioning properly, faulty engine ground, faulty battery ground, faulty torque converter, or the least likely option; a faulty or overly sensitive engine immobilizer. I have an idea on how to begin fixing it, but I have extended warranties that I do not want to void.