Wow that is strange. I'm going to assume the drums are MIDI which is why you are hearing them though.

The next thing would be to check if your RealTracks installation is OK.
If you right click on your RealTracks folder (in the BIAB folder) and do "Get info..." the size should be very large (mine is 54.5 Gb, I have the everything pak installed). If the size is less than that maybe not all your RealTracks got installed.

Next I would open up some of the sub folders in the RealTracks folders and double click on some of the .m4a files to make sure they play, or if you have 10.6 or 10.7 you can highlight the file and hit the space bar to hear them in Quicklook.

Do you have more than one account set up on your machine ?
If so you could log into another account to see if you get any sound out from BIAB.

Do you have the hard drive version of BIAB or the DVD installers ?
If you have the hard drive, I would try running the program from the external drive, or if you have the DVD's you may have to re-install the RealTracks individually.

Hopefully this helps.

- Jay

MacPro 5,1/12 core@3.46GHz -- OS X 10.15.7 -- ATI 7970 -- 32 Gig RAM -- Crucial 500GB OS SSD -- Samsung EVO 1TB Audio/Sample SSD -- BIAB 2024 -- Logic Pro X -- Cubase Elements 14 -- Too many plugins