Does anyone have a reliable way to convert google earth .kml or .kmz to seeyou .cup file format?

I've tried the GPSBable program but it keeps giving me an error "No Valid waypoints/routes/tracks translation specified". So apparently it does not read the .kml input file, but I can reopen it in google earth and it appears to be valid.

GPS visualizer seems to make a .gpx file format but SeeYou cannot open it.
http://www.gpsvisualizer.com/map_input?form=googleearth
Does anyone know what file specifications are needed for SeeYou gpx input?

Oddly I had this work last week but not this week.

The fact that SeeYou cannot import and export .kml waypoint and track files is a big lost opportunity.

Chris