I found very few posts similar to this topic, so I wonder if others have this problem?

Out of the box, the Fuze (4Gb version) seems to cause version 11 of Windows Media Player (WMP) on Windows XP to fail to synchronize songs (ripping from any CD) onto the Fuze about 95% of the time for me.  An error icon appears by each song in the sync results list of WMP.  Clicking the error icon shows a long error message saying something like "Cannot access file" or "no permission" to write to the device's file system.

Investigating further, I found a workaround to the problem and explain here. 

But first, I should note that I did find a newer version of firmware for the Fuze at http://www.sandisk.com/Retail/Default.aspx?CatID=1376
and I updated my Fuze --but it didn't fix the problem.  At this time (Feb 2009) it appears there are two versions of the Sansa Fuze (4Gb ver.) which each require a different firmware update (a series 1x and 2x) and mine is the earlier(?) 1x version.

I am new to the whole WMP/Music Player world, but it seems odd that two apparently completely different (and overlapping) file systems are used on the Fuze (and other players too).

If you look on the Fuze under "System Settings --> USB Mode" you get a choice of "Auto detect", "MTP" and "MSC" modes.  Using Windows XP, "Auto detect" always picks "MTP" mode.  Setting the Fuze to "Auto" or "MTP" gives the same result.  But when in this MTP mode, Windows Media Player will almost always refuse to synchronize ripped CD songs from the computer library to the Fuze, giving the error mentioned above. 

In this Auto detect/MTP mode, when it works, the album artwork gets copied over.  That seems to be about the only advantage I can find to using this Auto Detect/MTP mode. 

Further, when (in this MTP mode) I browse to the Fuze directly using Windows Explorer (that is, open the Windows "My Computer" icon), I see the "MTP" filesystem, for lack of a better term.  The "Music" folder --and notice it is spelled with lowercase letters, contains only the albums copied/synchronized by WMP to the Fuze while in the "Auto detect" or "MTP" mode.  Also noteworthy, trying to create a nested folder in a folder inside this "Music" folder (using Explorer) will also fail, and gives a similar error message about "no permission" to write to the file system.  And it doesn't matter if I'm using a Windows XP normal or Admin account.

THE ONLY WORKAROUND that I found to these too-frequent synchronization failures using WMP with the Fuze:  Change the USB mode on the Fuze to "MSC".

When I do this, every song synchronizes every time, no problem.  But, I don't automatically get the album artwork onto the Fuze anymore.  But I can work around that (for now) by using Explorer to manually copy the artwork file "Folder.jpg" that WMP puts into the rip folder for each album, from the computer to the Fuze.  Later I'll try configuring WMP to rip CD's directly to the Fuze and I think that will take care of the artwork problem too.

When the Fuze has the USB mode set to "MSC", the Fuze looks like a disk drive in Windows Explorer, with it's own drive letter, and it behaves like one.  Except that you see a completely different set of files --the "Music" folder is now spelled "MUSIC" (all uppercase) and none of the files or songs that were copied/synchronized when in the other "Auto detect/MTP" mode show up, just the ones copied/synchronized when in the "MSC" mode. 

It seems like there are two completely different file systems, each with their own files/albums/songs etc., and each file system can only be seen in Windows depending on which USB mode you set before you connect the Fuze to the computer.  But when using the Fuze by itself, it shows the two sets of songs & files merged together when displaying the list of songs it has.  So you can end up with 2 copies of the same songs on the Fuze, one put there using MTP mode and the other put there using MSC mode. 

What a mess.  This "Auto Detect/MTP" mode/filesystem would have been a OK idea, if it had been made to work properly to begin with, but it seems to cause so many errors for me that I find it better to set the Fuze to MSC mode and stick with that. 

Your experience may vary... (maybe if your Fuze has the "2x" series firmware on it).