In the last few days, the Google Map interface has a completely new look. Part of that change has rendered the GmapToGPX script useless. It was already partially useless because you would have to enable running external scripts. This was an extra step, and required you to re-setup the map page you had just perfected.
There is an easier way!
GPS Visuallizer provides a conversion page for making a Google Map page into a GPX file, or Google Earth file (KML).