Help Bluetooth doesn't work while speaker is connected

[rute]

I have my car paired with my S2 Bluetooth. The other day I connected the speaker out on the S2 to the audio-in on the car stereo. I received a call while listening to an audio book on the phone. The car muted the audio in and answered the call. I could not hear the person calling. I think the phone was trying to send the sound out the speaker rather than the Bluetooth. When I don't have the phone speaker connected, Bluetooth works correctly. Is this a known problem? Is there a way to fix it, maybe a setting I'm missing?