[HTC Rezound] kkozma:
I have no idea if you're barking up the wrong tree or not, but I just spent some time out in my car with my laptop and logcat.

I found the following when I tried to receive a call:

I/AudioHardwareMSM8660( 142): Routing audio to Bluetooth PCM
E/AudioHardwareMSM8660( 142): unknown stream
D/AudioHardwareMSM8660( 142): new_rx = 37
D/AudioHardwareMSM8660( 142): new_tx = 38
D/AudioHardwareMSM8660( 142): Starting voice on Rx 37 and Tx 38 device
E/AudioHardwareMSM8660( 142): value of device and enable is 2 0 ALSA dev id:24
E/AudioHardwareMSM8660( 142): value of device and enable is 3 0 ALSA dev id:4
E/AudioHardwareMSM8660( 142): value of device and enable is 17 1 ALSA dev id:37
E/AudioHardwareMSM8660( 142): value of device and enable is 18 1 ALSA dev id:38
D/AudioHardwareMSM8660( 142): updateDeviceInfo: E
D/AudioHardwareMSM8660( 142): The node type is 1
E/AudioHardwareMSM8660( 142): value of device and enable is 2 0 ALSA dev id:24
E/AudioHardwareMSM8660( 142): value of device and enable is 17 1 ALSA dev id:37
D/AudioHardwareMSM8660( 142): updateDeviceInfo: X
D/AudioHardwareMSM8660( 142): addToTable stream 3
E/AudioHardwareMSM8660( 142): ioctl TPA2051_SET_MODE failed: Invalid argument
D/AudioHardwareMSM8660( 142): setVoiceVolume(1.000000)
I/AudioHardwareMSM8660( 142): Setting in-call volume to 0 (available range is 5(MIN VOLUME) to 0(MAX VOLUME)
D/AudioHardwareMSM8660( 142): AudioStreamOutMSM8x60::standby()
D/AudioHardwareMSM8660( 142): Deroute pcm stream
D/AudioHardwareMSM8660( 142): deleteFromTable stream 1
E/AudioHardwareMSM8660( 142): write(): dec_id = 1 cur_rx = 17
E/AudioHardwareMSM8660( 142): cur_rx for pcm playback = 17
E/AudioHardwareMSM8660( 142): value of device and enable is 17 1 ALSA dev id:37
D/AudioHardwareMSM8660( 142): addToTable stream 1
I/AudioHardwareMSM8660( 142): Routing audio to Handset
D/AudioHardwareMSM8660( 142): setVoiceVolume(1.000000)
I/AudioHardwareMSM8660( 142): Setting in-call volume to 0 (available range is 5(MIN VOLUME) to 0(MAX VOLUME)
D/AudioHardwareMSM8660( 142): new_rx = 0
D/AudioHardwareMSM8660( 142): new_tx = 1
D/AudioHardwareMSM8660( 142): updateDeviceInfo() called for default case
D/AudioHardwareMSM8660( 142): updateDeviceInfo: E
D/AudioHardwareMSM8660( 142): case VOICE_CALL/VOIP CALL 3
D/AudioHardwareMSM8660( 142): acdb_loader_send_voice_cal acdb_rx = 7, acdb_tx =4
E/AudioHardwareMSM8660( 142): value of device and enable is 17 0 ALSA dev id:37
E/AudioHardwareMSM8660( 142): value of device and enable is 18 0 ALSA dev id:38
E/AudioHardwareMSM8660( 142): value of device and enable is 0 1 ALSA dev id:0
E/AudioHardwareMSM8660( 142): value of device and enable is 1 1 ALSA dev id:1
D/AudioHardwareMSM8660( 142): The node type is 1
E/AudioHardwareMSM8660( 142): value of device and enable is 17 0 ALSA dev id:37
D/AudioHardwareMSM8660( 142): updateDeviceInfo: X
D/AudioHardwareMSM8660( 142): setVoiceVolume(0.800000)
I/AudioHardwareMSM8660( 142): Setting in-call volume to 1 (available range is 5(MIN VOLUME) to 0(MAX VOLUME)
I/AudioHardwareMSM8660( 142): Routing audio to Handset
D/AudioHardwareMSM8660( 142): new_rx = 0
D/AudioHardwareMSM8660( 142): new_tx = 1
D/AudioHardwareMSM8660( 142): Ending Voice call

This is interesting. Tried it a few times and without fail when I answered the call, I got the same error.

ioctl TPA2051_SET_MODE failed: Invalid argument.

*edit* The error appears whether connected to BT or not as long as BT is turned on however, it does NOT appear when BT is turned off.