There is a technical service bulletin on this problem. The release switch in the shifter has malfunctioned. Replacement of the shifter is required to fix your problem.
April, 22, 2011 AT 2:05 AM
I ordered a.250 dia 60" piece of Delrin from McMaster Carr for a few bucks. I made a great replacement peice. Drilled the hole for the shaft, flatted and widened the end that mates to the spring to make sure the spring wouldn't slip over the shaft. I cut a slot on the top end parallel to the shaft hole so you can align the shaft hole during installation.
The Delrin is very flexible and very strong. The shifter feels very solid and works great. Pretty easy fix actually, if you can take it apart you can fix it!