Quite querulous... What format of song is it? I had a few MP3 that did the same thing, so I converted them through the Advanced menu and now they're fine. Notably, I converted them to the same format and bitrate that they already were, as anything else would have seen a larger drop in quality. You can change these conversion settings in the iTunes Preferences, under Importing. Converting the song creates a new version, and this new version played properly for me. I then deleted the old version. 🙂