I just tried panning in RB and got the same results. I have an acoustic bass track that shows in the tracks pane to be a mono track. But when I hit play and switch to the mixer screen, it shows the track to as a stereo track with a distinct left and right channel on it and a peak indicator assigned to each. When I attempt to pan hard left- nothing but I can still see the left channel peak indicator bouncing up and down . As I start inching the pan control toward center, I start hearing something. At center panning, both the left and ran indicator move. The farther I move to the right, the volume doesn't change but the left peak indicator decreases and finally stops working altogether at hard right.

And Mac, I'm using Sonar X2 Producer.