ActionScript 3.0 :: SecurityError: Error #2121: Security Sandbox Violation

I'm currently playing around with sound visualization in Flash and AS3,Anyway, I'm using this code:

PlayMusic.as
ActionScript Code:
public class PlayMusic {   
private var sound:Sound;

[code]....

I'm certain the path to the mp3 is correct, it starts playing, but here is the wierd thing, when I'm running it I get a steady stream of these:

ActionScript Code:
Error: Error #2030: End of file was encountered.
at flash.utils::ByteArray/readFloat()
at classes::DocumentClass/loop()

And if I just remove this line "t += ba.readFload();" I instead get zeroes (from the trace(t)-line) mixed with:

ActionScript Code:
SecurityError: Error #2121: Security sandbox violation: SoundMixer.computeSpectrum: file:///Macintosh%20HD/
Users/myuser/path/to/swf/main.swf cannot access . This may be worked around by calling Security.allowDomain.
at flash.media::SoundMixer$/computeSpectrum()
at classes::DocumentClass/loop()

And well, as if that wasn't enough, if I try and run it a couple of times the whole application just crashes (not only the swf, but Flash CS4 too).

System info:
Macbook Pro 15" 5,1 (latest edition)
Running Mac OS X 10.5.5 and Flash CS4 (10.0)