I had the same problem a few months ago and listed it under a 2000 GP. When I changed the actual electrical ignition switch, cost of $100 for the part, all of the problems went away. If you are not able to "override" it anymore by pushing the plunger from under the column, then you may also need to change it which it is called the lock actuator which is most likely a dealer item.
Monday, May 7th, 2007 AT 2:21 PM