Well, I am using ALSA, but I think that it still interacts with aRts somehow? I'm not sure. I'm running Fedora Core 1 with a 2.6.4 kernel.
I should note that in addition to the realplayer incident, this always happens after I burn a CD with K3B and it plays the little "success" noise. A few seconds after the sound, I get an aRts server overload error.