I´ve got the same problem. It only occurs when not driven for a while - eg when cold. Test your car like this: first, secure the car by the mechanical brake. When the starter wont respond, keep the key in starting position and move the shifter slightly. Not as far as into R, of course...

Haven´t got shiftlock on mine but this simple test might work anyway. If the starter responds when you move the shifter, something´s wrong in the protection circuit - probably the gear position switch or it´s alignment since the switch controls the P/N starter power.

Just wish I had that warranty, too...

/Martin