Hi. My daughter’s e260 got this error on many songs we had downloaded as well. I found that it was related to the Rhapsody music we had downloaded. As soon as I deleted ALL of the files associated with Rhapsody, the synchronization message never appeared again. If you have Rhapsody music on your player, maybe you could start there.
WalMart’s tech guys are super-nice…they helped me re-downlaod the music we were unable to use due to synchronization error at no charge. I am not a big fan of Rhapsody, since we cancelled the free trial subscription within the cancellation period, but they continued to bill us even though the songs had stopped working (same sync error). It has been a bit of a mess.
Good luck!
