GPS Unit dismounts - anybody got a fix?

Basically my girlfriend and I both have GPS units. I have a Garmin and she has a Bryton. We have supposedly downloaded all the latest software off the respective websites, but when we try uploading the information to a Mac the remote drives disconnect. Apart from the disconcerting messages about damage to the device it is incredible frustrating. When I upload to a PC I have no problems. I used to be able to use Windows on my Mac (using parallels) to upload, but due to a software update this is no longer possible. I was wondering if anyone else has had a similar problem and how they solved it.

The Garmin website is particularly annoying in being able to access any useful or meaningful information. Any help is appreciated.