My gpx track also have lost trackpoints at the start of the hiking. Maybe that is the problem of both tracks. For the moment I didn't have the opportunity of trying again in windows.
Hi, I want to report that I have also Rainer's problem. In my case my gpx file works in Linux but fails in Windows 7. I attach my gpx file to see if it helps. The track has been done using a nexus 7 and track@way (http://www.trackaway.org/) as software.