You have a failed membrane keypad.

If you (or someone you know) might want to replace it yourself, I have uploaded a handy guide with pictures showing you what's typically involved.

You can usually find helpful exploded view diagrams and order parts by entering your full model number here.

There should also be a "mini-manual" hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting & testing.

If you would like to have us do this for you, we do that for $39.95 plus part costs.

Feel free to contact me directly (and please remind me of your model number) for more information & help.
We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

William E. Miller
[email protected]
http://www.microwavedisplay.com