Well, got it working - sorta…
I updated the firmware to the latest version and did a format (lost 78 songs - not all of them backed-up).
But now it appears that it works correctly only if the USB Mode is set to MSC.
Using Windows Explorer, I drag/dropped some music files (mp3) into the Music folder. They showed up in Windows Explorer and they played properly. I fired up the NetLibrary Media Center to download an audiobook. But it does not detect that the Fuze is connected to the computer.
I changed the USB Mode on the Fuze to “Auto Detect”. When I did this, the NetLibrary Media Center detected the Fuze. But, the music files that I had downloaded were no longer visible in Windows Explorer. IOW, I was back to the original problem. I changed the USB Mode to MTP - the behavior was exactly the same. Apparently, “Auto Detect” simply uses the MTP mode.
So, I changed the mode back to MSC. I used NetLibrary to download the audiobook to my computer and then manually copied the downloaded files (they’re MP3’s) to the Fuze (dropped them into the AudioBooks folder). The Fuze plays the files ok.
So, bottom line is: MTP mode does not work correctly. MSC mode does work but requires that any file downloads be done manually.
Any thoughts as to what the problem might be here?