Software :: Unexplained Airtunes / Itunes Pauses

almost everytime I use airtunes, somewhere in the middle of a song, the music will quit unexpectedly. sometimes the music will resume in a three-count, sometimes longer, sometimes not at all. When i look at itunes, it looks like the song is just paused - meaning the little diamond that shows where you are in the song in the display along the top isn't inching along anymore, however the actual PAUSE button on the upper left has not been selected (meaning there is not a PLAY arrow displayed. the double bar PAUSE button is still showing). I have tried:

stopping the song (clicking the PAUSE button) and then starting it again
quitting itunes and restarting
restarting my ibook (G4)
unplugging my airport express and plugging it back in to reboot
using the airport admin aplication
completely unplugging EVERYTHING (modem, airport base station, airport extreme) and then slowly rebooting them all in order
upgrading itunes to the current version

at first, I thought it was a problem with airtunes, like the signal got lost or something, but after looking at itunes and realizing the song isn't *going* anymore, i thought the problem was with the application. but I don't know. I've never experienced this if i use the computer speakers, but then again, I hardly ever use them so I really don't know that for sure. oh, and I bought my airport base station *after* the airport express, and I'm pretty sure this problem was happening when my "network" was just my ibook and the express. (my experience level: I'm a former PC'er. I'm fairly knowlegable, but more on the software end. I know *nothing* when it comes to mac hardware.