Check the Volume and Panning on each instrument. You will probably find that they are defaulted to 0 (no volume) and -63 (panned right) respectfully. This is a known bug. I just imported a midi file and it came in as I described so it seems they have not fixed it in build 16? You have to manually turn things up and pan as desired then save the BITB file. P.I.T.A. I know.