If you are using ASIO sound drivers with your soundcard, make sure that the "ASIO Always On" is checked in your Audio Settings. That button is located at the bottom RH area of the Options->Audio/MIDI Settings window in BIAB.

Try it both ways, I have one laptop running Win7 that seems to work better with that UNchecked.

I can play my keyboard when the song is stopped after first hitting Play and it stays that way for a full session as long as BB remains opened. If I close and reopen BB, I have to do that Hit Play routine again to get it back when using a softsynth as sound source.

When the ASIO Always On is checked, I have certain other recording programs that won't relinquixh or regain the ASIO drivers if they are opened and running at the same time as BB. I just change the other program to use the Windows Sound drivers for that session.

--Mac