My Dakota 20 works fine with the same cable.Putting the s-d card into the etrex 20, after sending cache to my gps which finds the s-d card and downloads the gpx file to it. The unit then locates the cache on the gps map and all other functions work.
I go to geocaching .com, find the cache I want,open it and click on the cache I want. Then send it to gps by clicking on sen to gps. my card is found,clicking on write downloads the corordinates to the card. Put the s-d card back in gps and it will find that location and direct you to it.
I guess i do use a browser to do the work.
blksmith