So I would also like to upgrade the firmware of my 255W, but at present I'm locked out of it. I have a Garmin Nuvi 255W that had the original NA maps installed. Last week I put an SD card into it and updated to the current NA map installation. It worked fine for one trip out in the car, but then when I connected it to my computer, everything went wild. Windows 10 kept asking me to insert a removable USB drive over and over again until I removed the GPS. Unfortunately I didn't safely remove it. So now it just stays stuck on the "Loading maps" screen when it's not plugged into the computer, or it just stays stuck on the computer connection screen when I connect it, without ever becoming visible to Express or Windows as a USB Mass Storage Device. I've done all the regular things to try to get access to its file system (different cables, different computers, different computer ports, making sure the battery is charged), without any access to the device. So then I downloaded Updater, and tried to gain access that way. I opened a Cure file with Updater, connected the GPS and held down the upper left corner of the screen, saw that Updater recognized the device and right away tried to begin the flash process, but every time I do this, instantly when I hit OK in Updater, the connection with the GPS is dropped before the GPS can be flashed. I've tried many different combinations of actions but no success. I'm wondering if a different cure file would work. I'm using 082701000610cure. Once I gain access I'm planning to use 08270100061.rgn to properly flash the firmware after I delete the maps that seem to be causing the problem. I've also tried using Updater with the OUT.rgn file mentioned above. I don't believe the unit is "bricked," but any help would be appreciated.

Oh it's 'bricked' alright. That is, it's soft-bricked, and almost certainly by the recent NA mapping you installed. You mentioned an SD card being used for that update however if the entire mapping was placed on the card and then some corruption caused the device to stick on "Loading Maps", simply removing the SD card would allow the device to boot normally, albeit without a current detail map.

Please supply some more info if indeed the device is still stuck on loading maps without the SD card inserted, specifically: How did you update? i.e. With GarminExpress to obtain 'official' mapping as an IMG from the Garmin server. Or is it 'unofficial' (unlocked) mapping either as a ready-compiled IMG file, or one made from a GMAP folder (PC Install version) using MapInstall or MapSource (the latter is know to cause problems with modern NT map data due to it's older algorithm not being completely compatible whereas MapInstall is completely compatible with such data).