Tried Nuvi 255 with SD 2gb, and it refused to accept Western Europe map update.
Garmin express asked for 16gb, even though the maximum card size supposedly 4gb.
What is the true maximum card capacity and type for this device?
Folks, the memory card might not be your problem. I am using a SanDisk Ultra 32GB microSDHC UHS-I with the SD Adapter and it reads it fine on the 255w! (Make sure you do the firmware updates using the garmin express) To see if it is reading your SD card, do a test: Create a folder in the SD called Garmin, then create a folder under that called JPEG and place a jpg file in there. Then try to view the picture from the picture viewer in Garmin. If you can view the picture then your SD card is fine. If you downloaded an update img file (gmapprom.img), place it in the Garmin folder you created in the SD card and rename it to gmapsupp.img and it should be able to read it. It needs to be renamed to gmapsupp.img if not it wont read it! Once you get this working you can rename the original file on the garmin from gmapprom.img to gmapprom.img.ORIGINAL so it wont even try to read it or use it.