Personally this has never happend to me, but I saw it a few posts ago on this thread, and read a while back also.
The switch on the brake pedal may have been bent or have fallen off to where pushing the brake pedal does not light up the brake lights or actuate the solenoid for the shifter to move... My brother told me a while ago that it was common on either T-birds or Mustangs for it to just pop out (especially with big feet).
So check the switch on the brake pedal.
