problem in using GRASS

I am a grass beginner. when I use it, I found following problem:
  
When two users ( say user A and user B) use Grass4.0 at the same time, one user can kill another's X graphic drive(e.g. driver x0 has been started by user A.
Use grass command "d.mon stop=x0", user B can kill user A's driver x0).
    
Can anyone help me?
    
Thanks

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   /************************************************/
   /* Haishan Huang */
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   /* LUTCHI Research Centre */
   /* Department of Computer studies */
   /* Loughborough University of Technology */
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   /* Email : H.Huang@uk.ac.lut */
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