Originally Posted by josh@z1

Does the car still roll with the trans in neutral and the parking brake engaged. Could be an easy way to check on a hill to make sure the parking brake is working.

Most owner's manuals state that on an automatic transmission cars to:
Park the vehicle
Put gear selector in Neutral
Set the Parking Brake
Let off the brake pedal
Set the gear selector to Park

The ones I have read state this to avoid the symptoms you have.

Otherwise take the car in for warranty.