Could it be that there's too much computerization controlling the Toyota drivetrain? Simple computers rarely, if ever, get viruses...but if you sneeze wrong on your PC, you could create a malicious program. at least, it seems that way.
It's starting to sound, from a lot of these "owner descriptions" that keep coming up, that there's a programming bug that causes these cars to do these things...particularly when the much-vaunted "Hybrid Synergy Drive" comes into play.
Toyota is a quality-oriented company. They invented production systems to ensure this. However, now they're writing software...which cannot be quality controlled in the traditional way, or even the Toyota way. a piece of software is copied over and over, perfectly the same, no variants. You can't see what's wrong with software until it does something wrong.
It could be that a specific number of inputs could cause a division by zero, which causes the car to think that's in cruise control and is set at infinity. Or something of the like. Whatever it is, Toyota needs to bring a Geek in and have it fixed.
[joke]They must have used someone from their Formula 1 effort to program it.[/joke]