What a tale of woe. And I am pretty good at sorting out these sorts of things.
Bought Express with Kingstong 2G microSD card.
Used it two days both in MTP mode and Windows Media Player 11 and in
USB mode with Windows Media Player 9. Did everything, copied files over
in both modes, deleted files, even created playlists. Synced with WMP 11.
Worked great. Not a problem. Firmware 01.01.01 (I believe that is what was on it,
it might have been something else.)
Wednesday evening decided (after much consideration) to go to Windows Media Player
11 on the laptop so I could create playlists on the road. I had installed the Sansa updater.
Updater runs, and I let it update the player to 01.01.01A with microSD installed
Immediately the player starts running very slowly and fails to show the microSD card.
Removing the microSD seemed to restore the device to operating normally.
But, since then:
I have seen “read only” files and directories created. Internal format.
Player displaying incorrect very strange media tag information.
(On files added as the internal drive was starting to get full.)
Not turning off.
Not turning on.
“No song” when the mp3 is visible and playable by WMP.
Seems like the player is not fast enough to display
information quickly as the 2G internal memory get close
to 400 songs.
Gave up entirely on USB mode and went to MTP.
Copied the music directory off. Formatted the internal
memory with the Express command.
Copied the files back on, joy! Everything looks good.
Songs are all there, display correctly, showing up in
the menus.
I do notice that sometimes a song shows up as no song,
and then a moment later the song is there. But it is working
well again. Also notice all the .dat files no longer exist.
I have about 250Meg free, so later in the day, add some more songs
and create a playlist.
Remove the player, does not turn on.
Hard reset does not restore operation.
Player does show up in USB mode, but not both the F and G
disks say “Please insert a disk into drive F:”, so it looks like the
Express can’t recognize/mount its own internal drive.
Inserting the 2G microSD card does activite the player, and the
building database scroll bar runs a few times, but then nothing.
Hard reset no joy. Power on, “Sandisk” for a moment, then nothing.
Hard reset for minutes. Hard reset with the player in a
USB port, drop and reconnects the device (but with still both drives empty).
Curious thing is pushing the power button shows “Sandisk” only once
in while, like the player is busy doing something else.
Well, at least it resolves the issue of whether to keep it. Now just a choice
between RMA and returning it for a refund.
Does look like the firmware has some problem with flash memory or
file systems that the prior firmware did not have. Or maybe an interaction
between some hardware issue in some players and the new firmware.
Or even a question of how much data is stored on the device, when I
had the 2G almost full, that seemed to cause problems.
I usually don’t have these sort of problems. Other people do and I go
“Oh come on!” 
I have seen every problem described …
-r
