Oh, also remembering an old bug with using .kmz files on a Garmin GPS, don't know if it was ever fixed. Those filenames may not work, I don't think the GPS would recognize the underscore character. I think you could only use numbers and letters. If you can't get them to work on the gps, try changing the names to something simple like bearswamp1970.kmz, with only letters and numbers.
But that was only an issue for using the files on a Garmin GPS, they should work fine in Google Earth and Basecamp without any change.