Just a thought - have you checked that your file path is still okay - I would have thought that something in the path may have changed when you copied it. (note that this function requires the use of an external file as compared with using angular brackets, try using a relative dos path e.g ".//Sounds//my_sound.wav").
p.s.
I just tried this suggestion, but it does not work!
Despite this, it gives no errors (i.e sound file is found but nothing plays).
Ed