Sanso c250 "syncronize to complete you music subcription" message

After loading 250 songs, most of them won’t play and I get an error message saying:

“Sycronize to complete your music subcription”

http://forums.sandisk.com/t5/All-other-MP3-players/SanDisk-sansa-e-260-stuck-in-quot-syncronizing-to-your/m-p/233052/message-uid/233052/highlight/true#U233052