hi all i was in the same position as stinky, my switch showed a fair bit of corrosion on the dimmer spring, seems like this is a pretty easy part to fail given the amount of use. a bit of a clean up and it works though there is spot where it just refuses to work.
yours could be as simple as a build up of dust and crap....or not
i found the switch itself quite simple to fix. to remove the switch assembly there is a small button on the side of the switch housing that needs to be depressed while gently pulling out the shaft.
dean