Are you using ASIO drivers for both? ASIO will only handle one application at a time. I use ASIO for Sonar and MME for BiaB and everything works fine.

Also MME for both BiaB and Sony Acid should work.

I hope this helps.

Whenever I get something stuck in the back of my throat, I dislodge it by drinking a beer.
It's called the Heineken Maneuver.

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware