This could be a file permissions problem for you. I had the same error and was able to fix it by right-clicking the file referenced (in Windows), choosing Properties, then unchecking the “Read Only” checkbox and pressing OK. Note: I copied files using Sync Toy so I changed the permission on my server and the source MP3 data files so that it won’t happen again – Sync Toy actually preserved the file permissions when copying. Fortunately for me, out of 18,000+ songs, only one song had this issue.