From TMan's lookup script:

0xC004101E is "Read-only file system" (Player error)

Sounds like the player may have rebooted during the song upload. Or, by any chance, did you recently add some new programs which are @EXEC'ing from /drive0? If you exec something from /drive0 in AC mode, the synchs will fail because the drive can't be unmounted and then remounted read-write.

And yes, hard disk trouble is possible, too. Have you had any of the other symptoms of disk trouble?