I had a look and the RealTracks from 2011 up seem to use the
bt1 beat file instead of the bt0 that it's looking for.
Have you got 2011 or 2011.5 ?

Band-in-a-Box® Version 2011.5 Update - Build 329 (Aug 25 2011)
Band-in-a-Box® Version 2011 Update - Build 319b (Aug 22 2011)