I have kernel 2.6.18.1. I recently upgraded alsa both in the kernel and
userland to 1.0.13.

Running btsco and kernel module without a recompile causes this:
kernel: EIP: [<f992054c>] snd_card_bt_sco_playback_open+0xac/0x110
[snd_bt_sco] SS:ESP 0068:d3d01e40

Solution was to recompile btsco and snd-bt-sco module.

However, now no sound issues from the headset and no microphone is
picked up.

aplay -B 1000000 -D plughw:2 podbay.wav completes but nothing comes out
of the headphones.

hcitool info for the headphone is:
        BD Address:  00:12:EE:E0:AB:CA
        LMP Version: 2.0 (0x3) LMP Subversion: 0xe1b
        Manufacturer: Texas Instruments Inc. (13)
        Features: 0xff 0xfd 0x29 0x78 0x18 0x18 0x00 0x80
                <3-slot packets> <5-slot packets> <encryption> <slot
offset> 
                <timing accuracy> <role switch> <hold mode> <sniff
mode> 
                <park state> <channel quality> <SCO link> <HV2 packets> 
                <HV3 packets> <u-law log> <A-law log> <CVSD>
<transparent SCO> 
                <enhanced iscan> <interlaced iscan> <interlaced pscan> 
                <inquiry with RSSI> <AFH cap. slave> <AFH class. slave> 
                <AFH cap. master> <AFH class. master> <extended
features> 

btsco -v during a session provides this:
btsco v0.42
Device is 2:0
Voice setting: 0x0060
RFCOMM channel 1 connected
Using interface hci0
recieved AT*ECBP=?
recieved AT+CLIP=1
recieved AT+CSCS="UTF-8"
recieved AT*SEAM="HBH-610a",13
recieved AT+CLAN?
speaker volume: 10 mic volume: 1
i/o needed: connecting sco...
connected SCO channel
Done setting sco fd
recieved AT+VGS=6
Sending up speaker change 6
speaker volume: 6 mic volume: 1
driver is not in use
disconnected SCO channel
speaker volume: 6 mic volume: 1
i/o needed: connecting sco...
connected SCO channel
Done setting sco fd
recieved AT+VGS=6
Sending up speaker change 6
speaker volume: 6 mic volume: 1
driver is not in use
disconnected SCO channel

This worked previously before the alsa upgrade (required to fix a
problem with a soundcard).