Moo,
This is similar to something that I spoke about in a recent post. It sounds like you have frozen the Soloist. This is very easy to do because if you save a song in BIAB, it will automatically freeze and save the Soloist. As far as I can tell there is no way to turn this process off.
Have a read of my post and the fix that I discovered. It's
here.
Peter as advised us that he's working on it. In the meantime, if the error is the same one I played around with, to avoid it, simply erase the Soloist before the final save of a song and subsequent exiting of BIAB.
Noel