What the heck?

You go to Settings, check System Info, check number of songs in there. If they are existing, you should change to MTP or MSC to play it. Or go to Settings, Reset All, Yes. Try it.
If you accidentally formatted it, can't restore them.
Good luck

I've had this happen a couple of times in the last 6 months. You can get it to play again by chosing the format option from the settings menu. Of course, then you've lost everything you had loaded on to it. Download your music/audio books again and they will play.

the must be in 128 bits if it was more than dis then it will happens

Sansa MP3 players will not play iTunes songs. Only iPods play iTune songs. Visit Limewire to download songs that you can play on your MP3 player.

ok buddy...it might be problem with the storage.. try to format the player once.. now the player will be fresh... now download all the songs and try whether its working fine... if the problem continues try to contact the player manufacturer for replacement

Fixed my "dead" Sansa by opening the back, removing the battery then putting it back in. This appears to have rebooted the system and now it's working fine. No files were lost.

(I did try holding down the on/off button prior to this but got no response at all.)

if i were u id just turn it off,take out the battery and get a fresh 1 and then see what happens.........ive been having problems with my sansa to:)

Try this: disconnect the player from the computer, hold in the volume + button, and reconnect the player to the computer while holding the volume + button in. Keep holding the volume + button for an additional 5-50 seconds. Windows should eventually go into recovery mode and revive the player- it will pop up a window that says Found New Hardware Wizard.
-----
Download the Sansa Recovery Tool from the Sansa website.
Format - Erases Everything: Connect your Sansa player to the computer and open Windows Media Player. Click on the Sync tab. Pull down the drop down menu underneath the Sync tab by moving your cursor over the Sync tab and left clicking on the little black arrow underneath the Sync tab. Highlight "Sansa 1GB" (wording may vary slightly), and then select "Format." - this should erase everything.
Firmware Upgrade- Erases Everything: Get the latest firmware upgrade from Sansa - it updates the firmware and erases every song in the player all at once. Note: this method doesn't work if already have the latest firmware. Go to this website and click "Firmware Updater" to find out: http://www.sandisk.com/Retail/DriverDownloads.aspx
or
http://www.sandisk.com/DriverDownload/driverList.asp
-Tha Mp3 Doctor

Okay, here's what i've encountered:  songs that I downloaded on rhapsody, without purchasing, only lasted about 7-10 days unless i reconnected.  once my trial period ended, i lost all the songs.  songs that i've purchased i've had no trouble (although if you load them to the sansa immediately after download, you may get the same message.  its best to wait at least 24 hours).  good luck

Your device has to be connected to Rhapsody every 15 to 30 days to verify your account.

If you are connected and signed in, and still receive this message, you should contact Rhapsody Technical Support as the error is on their end. (866-597-5507)


Best of Luck.