Gentooer: I've seen that error lots of times, no idea what causes it, I'd be tempted to reboot the n8x0, then use "a2dp enable" and see if it works (in fact I no longer need to use a2dp enable, whenever I connect my headset it just works in a2dp mode (even after reboots/re-installs of bluez-utils) - I also got to a point where a2dp enable would disable, and vice-versa; confusing!)