On my system SuSE 9.2 Pro, KDE 3.3.2 i can run Real Player 10 just as a root. 
As user i get a message:
Cannot open the audio device. Another application may be using it.
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If i want to play music file (rm, rmj) with Helix Player i get a message:
The following components are required:
audio/x-pn-realaudio

Mitja