sound in port not working

well right now i am trying to record some audio directly from the headphone port on my ibook to the sound in port on my wallstreet. the wallstreet refuses to use the sound in port however when connected, and i have no idea why. i suspect the sound card itself since the right speaker is dead and the power connection already broken, but i think that the dead speaker is more likely the speaker itseld or the cable. so with the computers connected and the sound running on the ibook, why would the powerbook refuse to connect?