Cruise Control problems of the 2008 Infiniti G37

I have experience two occasions during stop and go traffic where the engine will rev up and accelerate. On those occasions I had to press the brakes hard to avoid hitting the car in front of me. I also changed gears to neutral. During both times I was in stop and go traffic moving forward. . . Not turning. I also tried using the cruise control. Was traveling in a toll road in motion. Had difficult setting once cruise control was on. . . It mysteriously shut off. This was not weather related as it was a hot clear day and I was traveling the speed limit of 80.