I found the same thing when using endomondo on a nokia n95, apart from taking ages to lock, it was usually fine when it did, but then no and again it was all over, so I took the plunge and got an Edge 500, its better, the bryton 35 the track was amazing, but its lack of support and the fact it can only be used on a web based application, I went for the Garmin, stuff like strava, really only needs times, though the elevation is usful, but is very different to the data I have, endomondo doesn't use elevation for any purpose, as far as I know, having said that i just popped over and they have updated their site, looks much better.