My Garmin did something similar to me earlier in the year; nothing quite as long, but a bumpy ride where a far smoother but slightly longer one wouldn't have taken as long. (Story here)

On Tuesday I had issues with another sat-nav, which I'd managed to put into pedestrian mode. This led to it giving lots of frantic inappropriate instructions...

It having been Bonfire Night earlier in the week, I've heard the old quip about Guy Fawkes, "the only man ever to enter Parliament with honest intentions" more than once...