Sounds like your control board is messed up. Might be worthwhile to have a pro check to see if there is any internal microwave leakage. This can really play havoc on the electronics.

To be blunt, the keypads on those maytag ovens "suck". What you can try is to remove the control pad and check the connection from the keypad to the control card. Remove the two screws securing the top grill then fold down and out. Remove the one screw securing the wiring cover grill and one from the control panel. The panel will then slide out and up. The keypad is attached with a flex circuit. The tabs on the connector pull up to remove the cable. You can use a mild detergent but you don't want to remove any coatings. Firmly reseat the cable and slide the tabs down to secure it. This MAY help, but in all likelyhood you probably need to replace the keypad. You can order the part through this site, make sure you specify white or black because it comes with the cover.