One problem related to software has been reported for the 2008 Toyota Prius. The most recently reported issues are listed below.
Interior instrument failure. Temperature app. 23 deg. F. Car started normally mfd came up fine. Main dash instruments failed to come on. No speedometer, gearshift indicator, fuel gauge, or odometer. All exterior lighting worked fine. Vehicle shifted into reverse and drove normally for about 15-20 min. When I parked and tried to turn off the car by pressing the power button the vehicle failed to shut down. Contacted Toyota USA and was informed that they rely on their dealerships for tech support. Went through manual drivetrain shutdown by pressing and holding the power button. Shutting down all accessories to limit accessory battery. Could not lock vehicle. Approximately 30 minutes later went out to the car and vehicle powered up as though nothing had happened. I believe that the temperature was the issue and there is some software issue that is not in the owners manual. Anytime you cannot turn off a vehicle there is a risk for an accident and or injury from an unoccupied vehicle. The dealership service dept. Theorized that the accessory battery may be low. But this would result in the car not bringing the main battery online. Toyota should address this issue .