Ray,

I had this problem a wile back and I did manage to fix
it accidentally. lol, well, one day i got mad at the button
that wasn't functioning well and pressed it as hard as
I could. From then on it just started to work fine again.
I don't exactly suggest doing this, but I think my button
was just dislocated or popped out, or something. Maybe
just a push in would do the trick.