gear shift trouble

it could be your brake switch. How well do your brake lights work?

The interlock is currently under recall. I had mine replaced and the new one started locking up in just 2 weeks. The original lasted 2 1/2 years before it started getting stuck. You have to take out the clip in the cup holder and stick a screwdriver in to release it.

Had the same problem. Took the car to CarMax (purchased it there in January 2010 - used 2006 Explorer Limited - v-8). Turned out the solenoid on the shifter was bad. Mine progressively got worse and worse. Shifter needed replacing. Total was about $350, but I had an extended warranty, so paid $50. I do not believe this has been recalled by Ford, as I have not received any recall notice and have the car registered on the Ford owners website.