Playing sound in Flash MX 04 - Pro

ok, i need some help on this one. I’m using Flash MX 2004 Pro and for some apparent reason I cannot play a sound that was imported into the library, thru code. The button is within a movie clip nested 3 times below the maintimeline, which im assuming wouldn’t matter. The only time the sound actually plays is if, within the button I add 450frames and dump the sound within the down state. The filename for the sound is “VO_1.mp3” Any and all help would be appreciated! Thanks