Mighty Mouse: tweaking down movement in trackball

The down motion on my mighty mouse's trackball all of a sudden feels like there's a pebble in there (obviously I know there's not, but that's what it feels like). Performance has also been affected as it often takes more effort to scroll down than usual. Left, right, and up directions work fine. Is there a way I can open it up and clean it to fix it? It might be dirty.

turn it upside down and rub the trackball on your mouse pad. use a qtip and rubbing alcohol to clean the ball. its a common problem with the mighty mice