Microwave Won't Work?

No buttons work on our microwave except the temp control and power button.
We have replaced 2 main control panels and the touch panel. The light comes on in the microwave and goes off when the door shuts. This is a built in microwave that has hardly been used, but is out of warranty. Any suggestions? At this point we have put so much money into it we are kind of committed. Does anyone know what else could be wrong with it? The start buttons and others don't work but the temp control and power button does. Sure would appreciate any help.