Are you saying that you were on single-player, then?
I see.
Sorry to have wasted your time. I guess I should have taken into account that I was using Forge and stuff before posting on the official bug reporting site.
Would it help to say that I was on Bukkit? Also, I have Forge and Optifine installed in the Jar
There is a bug where sometimes the game doesn't boot the sound engine correctly. Re-launching the game usually fixes it.