Ketch,
PO64 is "Vehicle Acceleration too high" The cruise control will disengage and is most likely caused by wheel spin due to ice/wet conditions. Try to reset your codes and see what pops up.
Have you ever serviced your brakes. By that I mean a complete flush and fill. Allante brakes on pre 1993 models can fail without much warning. If your brake light comes on PARK IT NOW! If you need furthur help, I can put you in touch with an Allante brake expert.