I don't know if this will help but if you plug the earphones into a PC, the sound is muffled until you hit the button. I've had to take the clip and force the button down so I'm not forced to keep pressing it.

Edit:
I was doing some testing with the N800 and I've noticed that when you press the button during an internet call it hangs up.
If the screen is blank (low power mode) and you press the button it wakes up the device.