yeah, you now see what's still really wrong with linux - all the so-called 'soundservers' can't work at the same time. KDE uses arts, and if realplayer doesn't (eg output directly to the soundcard) you can only heare realplayer. you might try to get realplayer to output to arts. maybe you can set this in realplayer, and there is some commandline option from arts itself for that - something like "artsdsp realplayer" and it'll pipe the soundoutput through arts.