Michelled picked up a Microsoft Natural Ergo Keyboard 4000 last year after using a similar model at work. It recently stopped working and I figured we'd have to fall back to a generic Dell keyboard.
I contacted Microsoft to let them know about the issue and heard back within a day. The support person asked me to try a few diagnostic procedures. When I told him it was still messed up, he said a replacement was on its way (it shipped a few days later due to low inventory).