I've been having the same problem you're describing. It's as if the computer is running too many things and the music stutters - the other night I was playing free cell while listening to iTunes. I thought it was every time I won/lost or made an illegal move (whenever a notification comes up). After a little while it became apparent that that was just coincidental. No Internet connection was being used at the time, as I was at a different house and didn't connect to the network.
My laptop is pretty old - 8 years or so, running Wnidows XP.
I haven't looked for an iTunes update. Maybe there's a new one? I think it's an iTunes glitch, or we just both have the same issue. Try a google search and see what comes up. It would really suck to have this going on during a reception!