Same thing happened to me a couple of months ago, in the middle of a snow storm! I had started the engine and turned on the defroster. Got out to clear the windows and the damn thing locked me out! Luckily my wife's office was only a five minute walk. But I was pissed!
It's only done it once, and I haven't found anything in the manual or online about the problem. If you find an answer, be sure to post!