
Motorola MPx220
Bluetooth and getting music to play in stereo
Your problem is that Bluetooth's stereo profile (called AADP, or A2DP) is a more recent development. Your phone's Bluetooth software was intended only for handsfree or headset profiles (monoaural). The phone's BT software (actually called a driver or stack) probably does not support the stereo profile.
Unless Moto offers an upgrade to their Bluetooth driver (unlikely) you're out of luck.