You may want to give this a try...
If all the cameras are placed in the same room then turning on a camera in one group should turn off other cameras in other groups. But this only works if all cameras are in the same room.
This is working with my 7 cameras and I haven't seen anyone else post that in fact it works for them. Please post back here if you give this a try and what your results are.
(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)----KDR