There is no real reason for one sound to not play while others do. They are all just wav files. A couple of things;
1) Make sure no files are missing or have gotten corrupted.
2) If you installed a custom sound pack, remove it and install the standard sounds.
3) Rename your "settings" folder and try it. If it works, then something in there has gotten corrupted. NOTE: This makes the game act like a new installation.