I had the same problem and Steven Demming called me with the following info:

You'll need part:
V8889300 ($2.00) - to replace just the button

or

WF306900 ($45.50) - to replace the whole button board

You could then do it yourself (though I must say that I personally would not do it - too many screws and boards to remove), or give it to a service provider.

[This message has been edited by chony (edited 11-13-2008).]