Hi Tigermom. They just stopped talking to the computer. The 605 was iffy from the start, sometimes the computer recognised it sometimes not, the company I purchased it from sent me a 705 in replacement, which was great for a couple of months then that just stopped being recognised. I sent back the 705 and paid extra then to upgrade to the 800 but with the same result. It did seem to be a major problem with them as there was a lot of talk on google and I don't know anyone now who is still using one. I thought at first it was because of being a Mac user but I had the 705 on my office PC. The routing was also odd, if we had a trip anywhere I would take my bike and Garmin with us and cycle home. I did some great trips but checking Garmin mileage with the car's Tomtom gave some large differences a ride from my brothers to home was 45 miles with stretches on major roads but it was only 30 to drive it with the TomTom and on much nicer roads. Pretty pleased with myself today the TomTom worked great and the juice pack lasted all day.