HRL described exactly a problem I had on a 2006 which overheated from loss of coolant due to loose radiator cap.
Caused a very minor leak in the head gasket, leading to white smoke in the exhaust in the morning after sitting overnight. It went away fairly quickly, once the water which collected in the cylinder overnight burned off. The problem got worse over time resulting in taking it in to have the heads removed and the head shaved to remove a low spot in the aluminum head caused by erosion from driving it too long with a bad gasket.
Carl
