LSS stands for Last Song Syndrome - when you just can't seem to stop singing a particular song that got stuck in your head, no matter how hard you try to sing a new one, you'll just end up singing the same lines from that song.
iPod: *singing* We ride... When we ride, we ride, it's until the day that we die.. Gawd, I can't stop singing that song. Its stuck in my head.
Zen: You just got the LSS.