Jump started a flat BMW 330 D Sport and now the sat nav/stereo unit is dead?

Jump started a flat BMW 330 D Sport and now the sat nav/stereo unit is dead although there is power as the unit opens and closes just no display or sound whatsoever. have tried disconnecting battery for 45 mins to hope it resets but nothing - and have checked 'plugs' at the back of the unit to no avail. Please help ;-)