His first season, in game 3, he fell akward on his arm after a tackle, hyper-extending his elbow (his elbow bent the other way), and he pretty much held onto the ball with one arm from then on..
Last year, after 400-some carries, he had 3 fumbles going into the last game of the season. Then he fumbled it 3 times on the last game: one he lost the rock, one the ball was knocked out of his hands, one was a shuffle pass that was low and behind him and hit him in the hip.
I am not going to say RW never fumbles, but I would say that his "fumble-itis" has been greatly exaggerated.