I was able to successfully download the Mac version using Firefox. I had to go back in and delete all the files I had downloaded previously, and now Basecamp opens and I can read the map! Hopefully the transfer of this map to my GPS, which I'll do in several weeks, goes just as easily. Thank you SO MUCH for the map, which looks great, AND your quick response to help me out. I use Basecamp a lot so I got nervous. I will look for a donate button for you - thank you sockmonkey!