OK, it happened to me.
My guesses are that: 1) the 8GB SanDisk MicroSD card had a glitch. This is my prime theory.
2) trying something with MTP mode and WMP for you all, which I never use, left some bad artifact
3) I got a bad file on there, even though everything has been run through mp3tag
But it was a serious mess.
Turn on the unit, and nothing in Artists or Albums except the letter V and the letter F, each of which then listed as [Empty].
Tried multiple soft resets (holding the power button 30 seconds)–same result.
Took out the MicroSD card–same result.
At home with the computer, connected Fuze with MicroSD card out, and saw I could read the albums in the internal memory. Ran ChkDsk/Error-checking just in case. Disconnected, and albums were all listed again correctly.
Inserted MicroSD, and Refresh Database froze. Shutdown, removed MicroSD, the unit itself behaved properly.
Put the MicroSD in a card reader for the computer. At first, it wouldn’t recognize it at all: “Please insert a card.” Eventually, after putting the MicroSD in and out of the reader and connecting and disconnecting the reader, got the card to show up in My Computer and ran ChkDsk/Error-checking on it. (No messages after checking.)
MicroSD back in the unit, Refresh Database still froze.
Card in reader again, the computer wouldn’t read it. Looked in Device Manager to see the computer’s card reader driver (Ricoh) had the yellow exclamation point. Uninstalled it, ran Add New Hardware, it reinstalled. Now it read the card.
Ran Error-checking again, which took much longer and maxed out the CPU (running at 95-99 percent for nearly an hour). Still no messages after checking. Returned MicroSD to Fuze. Refresh Database still froze.
Format time. Since both internal and external memory were readable, I backed them up onto an external drive. I deleted an .ini file from Winamp and an .xml file from Windows on the card.
Formatted internal memory, formatted card, returned the music to each–minus the last five albums added to the MicroSD. Everything running smoothly. Re-added the last five albums. And still running smoothly.
Conclusion: Something happened to that card. Whether it was the settings in those .ini and .xml files. or the flash memory wearing out, I just don’t know. But working methodically, and formatting, fixed it.