ARGH Bluetooth!

[GirlinContempt]

I've had my LG Chocolate for nearly a year, and with it a bluetooth headset. The headset has two modes. Mono, for phone calls, and stereo, for music.
I have been listening to music on this thing for a year with no problems.
Suddenly, today, when I press to switch the headset in to stereo, it's fine. It pops up stereo, I can hear my keystrokes in stereo.
I open the music player, and it plays on the cell speaker, not the headset.
I can not for the life of me figure out why.
I've deleted and re-paired the device, switched everything on and off a bajillion times, tried starting everything in every possible different order I can think of.

I just don't get it.
It used to just *work*
Argh.

[GirlinContempt]

1. :(