I know I'm a newbie here, so someone correct me if I'm wrong, for I have never had this problem, and have only had my Prix for a year, but....first I would check the fuses to see if there is a fuse for the Shift Interlock system. Next, I believe there is a cable that runs from the column to the shifter, or shift interlock motor? (I've never had my console apart, so I'm just guessing and offering suggestions here). I would check that cable, or more importantly, the motor that "releases" the shifter when the brake pedal is pressed and the ignition is on. In the mean time, you can manually override the system with a small screwdriver, there should be a small cover you can remove by the shifter, and then simply press a small a button when you want to shift out of Park that will override the system until you can figure out the issue.
Also...I know this may sound REALLY REALLY stupid...but I have had cars in the past "stick" in Park simply because they had rolled back HARD against the tranny, like on a hill without setting the Parking Brake. Try rocking the car back and forth while trying to shift it out of Park...its free and worth a try. Happened to me twice in my lifetime with Automatics already. Just a suggestion.