Okay, a few days ago I started to hear a thumping noise from the rear of the car, perhaps in the trunk. It is only noticeable at 70 mph or higher. It sounds like I locked my kids in the trunk and they are banging to get out (which they weren't... I checked ). I checked to make sure the rear seats were properly latched, and they were. I had the tires rotated and balanced (it was time) and the problem still persists. Anyone have any ideas or experienced this? BTW, I have about 5500 miles on the car.