In BETA2, we have introduced track filtering. The intention is that tracks should show the correct distance, and the strange effects you get when a GPS is standing still or is indoors should disappear. You seem to have run into some bug in this new filter feature.
You can enable and disable this feature. You do that under "Settings -> Track Visualization". After changing the setting you might need to refresh the page. By disabling the filer, you will see you old unchanged tracks.
We are interested in finding the error you get. Can you check the information you have in the "track_info_mod " table? And possibly compare it to the values found in "track_info" for equal "track_info_id". You can also do the same for "track_data" and "track_data_mod"
Or even better, if you can give us access to your installation (and database). If you send login info to us here http://franson.com/gpsgate/support.asp
we will take a look and make sure we fix this to the next beta.