concurrent GRASS sessions?

The question about one user B being able to "d.mon stop" user A's
monitor surprised me. I didn't even know that two users could run
GRASS on the same CPU. I heard it was possible and tried it after I
installed GRASS4.0 and didn't have any luck even getting into GRASS
much less starting a display monitor. Would someone tell me what I'm
missing? Thanks,
Erin O'Doherty
Rocky Mtn Experiment Station
USDA Forest Service
Laramie WY
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