Thank you for getting me straight on the differences between pre-boot and MSM terminology.

So, I used GarminCure3 to generate both cure and original rgn files from the gcd file link you provided (I think that is what I used before).

Although I can initiate flashing of both files using Updater with it showing 100% upload, when it goes to erasing, I always get the attached error message
[Only registered and activated users can see links. ]

I have tried used Webupdater. It finds the Nuvi1350, but stays stuck on updating. I am not sure where the update file should be in order for Webupdater to access it. I assume Webupdater is looking for the RGN and not the gcd file. But again, where is it looking?

When I remove the flash drive, there is nothing in the drive except for the hidden System Volume Information folder that was created when the drive was formatted using RMPrepUSB.