Marlo Thomas had to cancel an appearance at a women's business conference Friday in Seattle because of a whiplash injury suffered in a car accident earlier in the week. Thomas was being driven from New York City to Connecticut, where she and husband Phil Donahue live, when her car was struck from behind by a van, a Thomas spokeswoman said. The driver wasn't hurt but the car had to be towed away and Thomas needed a neck brace. She tried to continue working but overdid it Thursday and ended up in pain, the spokeswoman said. "It's serious enough to stop her from speaking, which is pretty uncharacteristic for her," the spokeswoman said of "That Girl."