It was an intermittent popping noise coming from the right rear of the car (07 coupe). Dealership kept the car for a week, basically tore the rear down, tightened every frame bolt, suspension fitting, and back seat brace - still had the sound. They finally located a bad weld in the right rear quarter panel near the shock mount. They reinforced the weld - no more popping noise! Work was done under the 4 year, 60,000 mile, warranty (which I am just about out of now).

 

I have a a clicking sound back there too, but mine is from the back seat latch not holding my back seat properly. I don't know why though, busted latch probs?

 

Most of the descriptions in this thread sound exactly like mine. I'm excited I found this thread and will take out the rear seats and maybe the trunk panels to find this cross member and attempt to fix the noise

Now, what's this "sun roof" problem I read about above? I might actually have that since I do hear the popping more towards the top/rear of the coupe.