Toyota is recalling over half of all the Prius hybrids they have ever sold to repair a software problem that can slow down or bring the car to a halt.  The recall includes Prius vehicles produced since early 2009.  
The problem with Prius’s software may cause some parts to overheat in driving situations such as accelerating from a stop which can cause the car to enter a failsafe mode, where it can still be driven while at reduced power. In some cases, the hybrid system could shut down and cause the vehicle to stop.  To date, no accidents or injuries have been reported due to the software issue.
Toyota Recalls Newest Priuses Over Software