Buttons no longer respond, have to mash.

Question

I've been using my Zen X-fi for about a week now and recently the down button and even more recently the right button(on the 9 button layout) have both stopped responding unless mashed down very hard, like a cell phone after you've used it for a year or so.
I was wondering if there is any way to fix this, or should I send it in for a replacement.
I have tried resetting it with no success.