OK!OK!OK!, I've GOT IT!
Totally by accident, I figured out that if you hit the extreme pan on the positive side (ie. 64), something weird happens. For some damn reason, it will NOT pan all the way to 64. Instead it will actually MUTE that channel and send it full blast over to the other stereo channel!
SOLUTION: set the positive pan to 63 and NOT 64. Weird bug man.. but at least it's working now.
Christ... I can sleep a little bit now.