I used Garmin MapInstall for the first time today with success. I have tried over the past couple of weeks to get it to work. I had attempted to install Utah, Idaho, Oregon and Washington maps on my Garmin GPSMap 60CSx. It would take a couple of hours. Or at least that is what the progress bar said it would do. It would eventually fail with an error.
I learned that the Garmin USB Drivers are slow on the Mac. Kinda funny thing, using the Garmin through a Windows Virtual Machine running on the Mac, it worked as expected. To make a long story short, I updated the maps using the SD card installed in my Garmen. I first removed the SD card from my Garmin by removing the batteries and extracting the SD Card. I inserted the card directly in my Mac. The Garmin MapInstall recognized the SD card as a place to transfer the maps to. Instead of a two hour process, the whole process took less than 10 minutes. I think it close to 5 minutes. I took the newly installed maps on the SD card and placed it back in the Garmin GPSMap 60CSx. Everything works now.