Only hearing right channel in MPC60 stereo mix

EIther I'm completely clueless, or I'm having problems with the stereo out on my 60. When I plug both the L and R cables into the stereo out jacks I only get sound from the right channel. When I try to adjust the pan on the individual notes, the sample only gets louder and softer within the right channel -- nothing ever comes out of the left side.

If it helps I'm piping the sound thru an mbox 2. "Mono" button isn't pressed.

What am I doing wrong here? Any way I can hear/record a stereo output via the stereo out on the 60?

Been reading this forum for years, but I can't find anything on this.

That sounds like a main out problem possibly. Unless your doing something wrong with your samples like making them Mono I don't know.