Rescue 911 Not Responding

A few nights ago during regular gameplay my Rescue 911 locked up with
the helicopter active and a stuck ball message.

"No worries" I thought, "i'll check switches and optos"

So I restart the game and receive a stuck ball message, then I try to
enter the menu.

This is where my real concern comes from. The test button works, and
brings up the menu. The part that keeps me from getting any further
is that the flipper buttons do not manipulate the menu, so I can't
even get it into a switch test.

Where should I start looking for the cause of this problem?