Just get some compact utility and test the sounds.rar file integrity (CD3).
See if the file is corrupted. I´ve got the same problem, smashed my head against the wall trying to find it and afterall i discovered that the damn sounds.rar file was quite corrupted enough to mess up all in game sound / music.
It could be (hope not!) your problem, too.
A advise: WINRAR does not detect errors in this file, unless you try to use the "repair" feature within.
