RealPlayer8 won't for just one user

Hi, RealPlayer8 on 8.1 is working fine for all users (family members) except one. When it starts the message appears "Cannot open the audio device. Another application may be using it." Sometimes it runs but there is no audio. If the "first-time.rm" file is clicked RP8 runs OK once and therefter not. I have to log out and in again. I have checked all the obvious settings and compared them with those for the other users but there were no differences. Any suggestions ? -- John