One problem related to carrier/rack has been reported for the 2007 Toyota Prius. The most recently reported issues are listed below.
This is not one incident, it happens whenever the road is slick (rain, or even sprinkler runoff!) or if I drive over a pothole--the power to the wheels is cut and the engine feels like it is going to stall. It is extremely difficult and nervewracking to drive while it is raining. The most dangerous times that this happens is when I am at a signal, making a right turn I need power to the engine to merge into traffic, and make sure that oncoming traffic is not interrupted. There have been times that I feel like my car won't "go" or hesitates when I need it to go! and if it's this bad in wet conditions, I would never even consider driving the Prius in snowy conditions. I have read that this is all due to a problem in the traction control system. Very unsafe!!.