Cannot Play or Delete Files from Sansa Fuze

I purchased a Sansa Fuze 4 GB MP3 player on 2/1/09.  I have been very happy with it until a few days ago.  I attempted to sync the player with Windows Media Player.  Instead of syncing, all my files were removed from the player.  When I disconnected the player from the computer. I got the following message:
     Not enough space for Music DB. Please free 90 MB.

However, Windows Explorer indicated that there were no files (other than some system files) and thus no files could be deleted.

I have an 8GB card in the player, and loaded files onto the card.  These files show up in Windows Media Player and can be accessed via the computer, however, I cannot get access to the files on the Sansa because as soon as I turn the Sansa on, I get the Not Enough space message.

I have no idea how to get the Sansa useable again and also cannot find any information about accessing files on the card when using the MP3 player.

I would appreciate help as soon as possible since as of now the Sansa Fuze is unuseable.  Thanks.

Run ChkDsk

to deal with the database problem.

Windows Media Player is a menace. Its default is Auto-Sync. So it must have synced what was on your computer (no music) to what was on the Sansa (your former music). 

One you have run ChkDsk, go to Settings and make USB Mode MTP. Connect, and Windows Media Player should pop up. Look in Options or Tools under Sync and UNCHECK Auto-Sync. 

Unless you really love Windows Media Player, switch USB mode to MSC, which makes the Sansa work like any other removable drive. Then drag-and-drop your music manually, and WMP won’t mess with it.