Annoying noise on audio when RAM-previewed

Hey,

I have a song that I am currently using in a comp and at the 3rd second of the comp there is an annoying "pop" wich does not appear in the song when played for instance in itunes, if I move the sound file, forward for example, the pop appears back aain three seconds in the comp, so I think it has nothing to do with the audio file, since the pop appears in the song always 3 second into the comp, even if I move it left or right?

I'm clueless,

Thank in advance,

Tom