Having trouble getting vehicle out of PARK

After reading these threads I feel like i must have a great Jimmy! But I do have a problem with the automatic shifter. When you apply the brake to release the transmission to get into gear from Park it sticks. If you rock the vehicle back and forth violently you can engage the transmission, shy of that you're stuck in park. The tranny itself is in great shape, but the safety mechanism for engaing it seems to be going out. When I depress the button on the side of the shifter I can hear a clicking noise behind the gage cluster. Any ideas???