I had the same problem but got it resolved today. It turned out the sway bar end link nuts were loose. Took a torque wrench to them and were all good now.

 

Any updates? What was the cause of the sound?

 

Im getting this problem too, and its becoming more frequent. I assumed it was my SPL endlinks, but they are nice and tight and seem to articulate fine... any more info on if it is the sway bar bushing itself? I have polyurethane bushings currently.

 

hm...no popping sound anymore...seems like it just went away :P