i've had this problem for the past year of owning these headphones and i finally figured out how to get around my specific problem...
in my case, when i press the button, a help page comes up that says "About Voice Calls" on the top of it....
so what i did was found the help file in
"C:\Program Files\Microsoft LifeChat\" called "LifeChat_wlc.chm"
and renamed the file to "LifeChat_wlc.chm_DISABLED"
(i didnt delete it just in case i needed it for future use)
-fyi this was done prior to setting the button up to automatically launch Windows Live Messenger