One problem related to ignition has been reported for the 2007 Toyota Prius. The most recently reported issues are listed below.
In 2010 (approximately), the dashboard display of my Prius would intermittently not display when the car was first started. This condition makes it impossible to know how fast the car is going, how much fuel there is, etc. I visited dealers and independent mechanics and no one claimed to know anything about this problem. However, I have subsequently learned that Toyota issued a service bulletin on this very issue in 2009! (t-sb-0172-09). I've also since learned (due to my own research) that the most likely cause of this problem is a faulty combination meter (as per the Toyota sb). One independent garage in san francisco, CA has even started a blog about this because they are seeing so many repairs for this condition! it is absolutely a safety issue and the problem continues in my car today (I've just discovered the potential fix of replacing the combination meter). In addition to the dash display not working, often other issues, such as the engine not turning off, key not releasing from ignition, and rear hatch not releasing are also associated with this problem. Toyota admits in its sb this is due to a faulty computer design from one of its suppliers but refuses to issue a recall notice. Nhtsa should force Toyota to address this issue as the problem happens not only at start-up, but sometimes while driving. Losing speedometer visibility is a serious safety issue; as is not being able to disengage power in the normal fashion.