Dave:

We discovered after a few tries that some USB drives don't work for the ClearNav, and possibly the Power Flarm. Previous posters have mentioned similar problems. In fact ClearNav first sent us a Patriot thumb drive and later told us not to use that make. Go figure! Another thing we discovered is that you cannot download the update on a thumb drive and put it on two devices: download it onto one thumb drive, install it, then download it again and install it on the second device. Fred