tl;dr - SD card should be formatted as FAT32
The past couple days I have worked to update maps (to North America 2015.40) on my nuvi 1450. Garmin Express seemed to work intermittently (ver 4.0.20.0 w/ Win 7 Pro 64-bit), and did say it fully installed the maps at one point. When I went to use my nuvi, only the very simplistic base map was available (crude interstates and highways) and the map info screen was blank. I then used Map Updater as suggested on a couple forum posts I read, which said that it worked, but the final result was the same. I could see and read the uSD card and see that the map image was on the card.
I called Garmin tech support today. They were very friendly and helpful. The cause appears to have been the micro SD card I was using, which I had previously formatted in NTFS format with a long volume name, not FAT32. I did a quick format before using the card, but didn't change the format type. I didn't see in any instructions that FAT32 was necessary. After reformatting to FAT32, Garmin Express worked smoothly after updating to the newly available ver 4.0.21.0. It was suggested to wait for ~30min after Garmin Express completed before ejecting the nuvi due to any delayed write procedures that may linger as a 'feature' of Windows 7. My updates were given more time than this over my lunch break. My nuvi is now working fine. This post is in hopes of helping someone else having unknown NTFS woes.
Garmin, thank you again for excellent customer service.
