I've started paying more attention since first having this problem. In my case, it *seems* to occur when I shift into reverse before the Borg collective approves, and displays the big message that it's OK to drive. The little green car on the lower right was lit, so I had assumed it was OK. But it sometimes takes a little while for the larger message to appear. If I don't wait for it, I get a check engine light, and the car won't respond. This seems a bit strange, because I had thought that it was impossible to shift out of Park until all systems were Go.