Try and reset the player first, If this does not fix the problem, Click this link to down load the Sandisk updater program to run a firmware update...Updater..
Resetting the device:
1. Press and hold the Power/Menu button for approximately 20 seconds.
2. Release the Power/Menu button.
3. Press the Power/Menu button again to turn on the player.
Next time you need to delete files heres how. --
There are two ways to delete files on your Sansa player. You can delete them from the player directly or using a PC.
METHOD 1 - Delete files directly on the device
1. In playback mode, press the Submenu button.
2. Select Delete.
METHOD 2 - Delete files using a PC
For all other Sansa players:
1. Connect your device to the PC.
2. Select Open device to view files using Windows Explorer on initial connection.
3. Locate the folder where your files are stored.
4. Click to select the files you want deleted and delete the files.
NOTE: If songs still exist after deleting, you may need to switch USB modes from MTP to MSC or vice versa. See this tip HERE
This error occurs when a Sansa player is almost filled to capacity. A Sansa player can NOT be filled to full capacity. (i.e. you can't put 2GB worth of songs into a 2GB player)
The player needs the extra capacity to create and maintain a "database", a database holds all the information such as playlists, recordings, song information, etc. The larger the amount of songs, the larger the database gets.
To resolve this capacity issue, you have to delete contents on your Sansa player using a PC.
STEP 1 - Delete files on your player
1. See first note on how to delete files on your Sansa player using a PC.
This error also occurs when there's a file system corruption in your Sansa player.
To resolve this issue, run error-checking to fix errors in your device using a PC
STEP 1 - Connect the Sansa player to the PC in MSC mode
STEP 2 - Run Error-checking to check and fix errors
1. Double-click on My Computer (Computer for Windows Vista).
2. Right-click on the drive letter associated with your Sansa player and select Properties.
3. Click the Tools tab and select Check Now.
4. Click both check boxes under Check disk options.
5. Click Start
If an error occurs while plugging in the player to the PC and some files are missing in the player, the database might be corrupted. To resolve this, you will need to format your player.
NOTE: Formatting will delete all files in the device. Your data (music, photos etc) is NOT recoverable.