We've got a weird one. Our 3-year-old lab suddenly won't come into the house through the doggie door. He'll go out through it happily, but on the outside coming in seems somewhat scared of it. He'll paw at it but that's it. He'd rather sit out in the cold at the people door and look at us. This came out of nowhere. Our only clue is that my wife said that the dog yelped when she touched his left ear yesterday, but he subsequently let my daughter thoroughly check his ears and there's no sign of injury. Any ideas?