Hi,
thanks for the report! The speed value comes directly form your gps unit so I think that probably your gps sends incorrect data to the woophoo client. Some Nokia receivers have this strange behavior.
Do you use an external gps unit? Does it work correctly with other applications? Can you please send the model number of it?
At the time the client does'nt verify the data, altough it is possible to calculate your speed using the distance between your recently measured locations. We will include this alternative speed measuring in the next release if the problem is really in the gps unit.