This is a stumper. A couple of more questions for you:

1. Are you running from your computers internal drive or a usb drive supplied by PGM? If internal, is it the same drive that BIAB is installed on?
2. Is it any bass real track and/or style or are you trying the same one for all songs?

Edit: Taking a look at the new update for RealTracks, it seems a lot of the fixes involved bass issues. Are you up to date with BIAB and RealTracks?

Barry