Why does my iPhone's audio when played over Bluetooth stop when the display turns off? [closed]

Why does my iPhone's audio when played over Bluetooth stop when the display turns off? [closed]

I've paired a Bluetooth headset to my iPhone and when I try to listen to music over Bluetooth with the display off, the audio stops when the display goes off, most of the time. Why is this? It makes the Bluetooth stereo audio of the phone pretty useless. I'm running iPhone OS 3.0, which added this feature.