HELP: Wild fluctuation in bluetooth volume!!

[cenozoite]

I have the Bell Mobility HTC Touch/Vogue and am using it with a Nokia BH-900 bluetooth headset. When making voice calls, the sound I hear from the other side oscillates wildly up and down about every two seconds. I've tested this with both people and automated phone lines, and in all cases it sounds like someone is turning the volume dial back and forth between 5 and 10 over and over again.

Does anyone know why this is happening, or whether there is any way to fix it? Thanks...