Still using my 500 even though I have the 520. It was working fine to work today, then I started a new lap to ride the three miles to the shops (sad, I know). Along the way, I noticed I was doing 100's of mph. Started a new lap on the return leg, which was fine. Uploaded the file onto Garmin Connect when I got home, and it shows a line heading into the Atlantic, and the three mile lap is 983 miles. Did an aeroplane pick up the signal or something, or the satellite it was connecting to suddenly change orbit?